I'm not quite sure which format would suit best for such a guide, so feel free to provide feedback and ask questions if anything in this guide doesn't seem very clear. Descriptions can be rewritten, screenshots added and updated, videos recorded if necessary.

There's a total of 77 red flasks in the game, each giving you +1 maximum health. You need to find 40 or more before the end of Drowned Veins to unlock the final weapon in the game - the ballista.
There are also 18 orange flasks in the game (one in each level). They increase the amount of ammo you can carry, and for each five of them you can have an additional emergency health potion.
Finally, there's a unique flaming bag upgrade in Sourwood that increases your sling damage by 50%.

You don't get anything special if you collect everything, but surely having extra health and ammo is nice, as well as immense satisfaction from 100% completion :)

In each section, flasks will generally be sorted in order of being able to collect them.

There are 6 red flasks and 1 orange flask in Deadwell.

Red flask #1
In a passage to the left of the witches' hut in the village.


Red flask #2
The exit from the village will open after you have talked to everyone and checked out the boulder near the church. Then, you can go through the woodsmen hut and across the bridge on your way to meet the Inventor. The flask is on top of one of the rocks past this bridge. You will need to jump onto the rocks to your right and then to where the flask is.


Red flask #3
The woodsmen will open a way forward after you acquire a sling from the inventor. Go past them on your way to the lighthouse. After you defeat the spiders, keep following the path until you reach an intersection. Go left all the way to find a red flask.


Red flask #4
Available after you discover an entrance to Deadwell from Greenslit. Entering from there, find a shortcut ladder and knock it down. Now you can try jumping to the hill directly ahead. Take a running start and jump from the tip of the rock on the right of the ladder. If you can't make the jump, you can get the flask later, after completing Haunted Glacier, as you will be teleported to that hill. The flask is next to one of the trees.


Red flask #5
This one and the rest only available after getting Ropewheel key. You will need to get a crank from Greenslit, ride down the elevator near the woodsmen shack and fight the ghost witch. Then, open the door in the witches' hut and proceed from there. At the bridge where the witch-daughter is waiting, jump to the plank on the left. Climb all the way up to find the potion.


Red flask #6
You need to cross the witches' bridge and follow the path until you arrive at the moving platform. Before riding it, climb down the rocks and search for the flask in the grass near the edge.


Orange flask
Ride the moving platform. When you arrive, go in the direction of the lighthouse. You will find the orange flask at the end of the cliff.

There are 2 red flasks and 1 orange flask in Forest Path.

Red flask #1
Proceed through the level normally. Eventually, you will come to a place where the path goes in between two ponds. The red flask is In the back of the right pond, behind a tree.


Red flask #2
This red flask is hidden behind a tree beyond the monster pond. You can bonk the pond monster's head to make it go away for a little while. When the monster isn't blocking the way, cross the bridge and look around past the statue.


Orange flask
You can find it after you break the barrier. Proceed a bit further and you should be able to see it clearly on the left of the path near a tree.

There are 4 red flasks and 1 orange flask in Ravenfen.

The mounds are numbered counterclockwise starting from the Forest Path entrance.

Red flask #1
This one is located right above the entrance to the first mound (the one that has the bow).


Red flask #2
You can reach this one from the way leading to the second mound (the one with the key). Instead of going down to the mound, keep left until you reach the end of the hill. Jump over to the other side and follow the path to the end.


Orange flask
The orange flask is near the entrance to the third mound (the one with the switch). Turn left before the statues and follow the path to the ledge overlooking the musicians.


Red flask #3
it's near the musicians, behind the pillar at the waterfall.


Red flask #4
To find it, walk away from the musicians back in the direction of the Forest Path entrance. Take the way down into the water. Flask is in the nearest bushes.

There are 9 red flasks and 1 orange flask in Greenslit.

Red flask #1
Found on a big rope hanging across the river. You can get to it shortly after jumping down from Ravenfen entrance. Keep going right to reach it. If you walk the rope to the other side of the river, you can go down some narrow stairs and planks to grab a crank, which you need for Deadwell. Since you're here, you might as well proceed on this side of the river and get a headlamp piece from a cave nearby and a coil of rope from the tower. Go back to the other side after, either going back to the rope or by using a bridge beyond the rope tower.


Red flask #2
If you stay on the right riverbank (the one that has Ravenfen entrance), you will eventually reach a couple of consecutive bridges. Cross them both and you will find a cave. You can grab an axe there, but watch out for an angry bear and some nasty bugs. This cave loops all the way back to the starting area of the level. Go through, cross a long bridge and then go down the stairs and jump down on the rock to your right to find a flask. You can also access one of the shields from here.


Red flask #3
Go back to those two bridges from before. From the little plateau in between them (the one with Nokkpond sign), go down the stairs. After descending, turn around and follow the path leading down to the river. The flask is in a bush behind the tree. While you're there, follow this path all the way to a cave and activate a switch, it will open the way to the haunted tower area.


Red flask #4
Go back from where you came and go the other way from the stairs. You will see a small tower with a bridge - that's what you unlocked with a switch. The flask is behind it, barely visible in grass.


Red flask #5
Enter the tower and cross the river. Keep right along the river and you will reach a big plateau with a moose, which has an entrance to the five shields cave. The flask is on the ledge to the left of the missing Nokkpond bridge, hidden in grass.


Red flask #6
Turn back and return to the entrance to the five shields cave. To the left of it there is a path going up. Climb there, then jump down to another ledge below to find another flask.


Red flask #7
At this point you can find a way into the trenches in the same general area. Fight through some nasty rock-throwing crabs and destroy the barrier. The way past the barrier will lead you to a pond (there's also a cave with a headlamp piece). Ferry across the lake, and you can find another red flask on the way leading to the haunted tower. Look around before you jump down to where the barricade was. If you have already traversed the pond and missed this flask, you are able to jump down to it from the ballista target place (you'll need to have found rope and pulley to ride there though).


Red flask #8
After you cross the pond, an underground passage into the haunted tower is available. Exit the tower before climbing to the top. There's a red flask under the staircase. Don't forget to open the shortcut to the tower.


Orange flask
There's an orange flask in the middle of the haunted tower. Try not to get stuck and eaten by the ghosts. Grab the shield from the top of the tower and use the ballista, if you got the rope before. You are still going to have to come back here again with the pulley.


Red flask #9
You can only get this one after you grabbed a pulley from Nokkpond (which in turn requires getting all five shields). You'll need to ride the line from the trilobyte signpost to the fortress area. After dealing with the bandits, go into the fortress and climb the stairs. Upon emerging on top, jump down to the ramparts to the left, then jump down over the fortress wall.

There are 3 red flasks and 1 orange flask in Trollhole.

Red flask #1
It's in the cave where the bait is. You can't miss it, it is in your way.


Red flask #2
Deal with the spiders and destroy the barrier. When you enter the next cave, look in the rocks on your right.


Red flask #3
Right before the entrance to the troll fight arena. Once again, can't miss it.


Orange flask
You will reach the rails shortly after defeating the troll. When you do, go right and you'll find an orange flask down there.

There are 6 red flasks and 1 orange flask in Nokkpond.

The 'first' lake is the lake with the Nokken. The 'second' lake is the lake that has a passage to Sourwood. 'Forward' direction is the way you're facing upon entering from Greenslit.

Red flask #1
It's on one of the dry patches in the first lake, near the shore closer to Greenslit entrance. The dry patch in question is around the middle. Beware the Nokken! It is best to run straight for it before Nokken comes closer. You can reset Nokken back to the center of the lake if you run far enough away from it.


Red flask #2
Go around the left side of the first lake on your way to grab the Otherside key. The flask is on one of the dry spots near the entrance to the swamp area. Try to get it on your way to grab the key, since Nokken will be most likely waiting for you on the way back.


Red flask #3
You can get it on the way to grab a pulley. Go around the right side of the first lake. When you reach a safe spot, turn right and go to the end of the cliff.


Red flask #4
So you survived the snake pit and obtained the pulley. Ride the long line over the first lake (you can get there through the shack that needed the Otherside key). When you arrive the other side, turn around and jump down (just don't un-alive yourself by accident). The flask is on one of the dry patches there.


Orange flask
To get it, keep to the right side of the second lake and go all the way to the end.


Red flask #5
You can get this one on your way to the bear crossbow. Just jump down to the ledge from the highest point of the hill before it.


Red flask #6
Keep to the left side of the second lake and go all the way to the end, beyond the goat lever cave. The flask is hidden in grass, almost invisible.

There is 1 red flask and 1 orange flask in Trilobite Tomb.

Red flask #1
You can find it in the first chamber of the tomb, on the right behind the statue.


Orange flask
Orange flask is found in the chamber with the drain and spiders. It's on the left side, behind a pillar.

There are 6 red flasks and 1 orange flask in Fallcrush.

Apparently it's impossible to go back to this level for the second time, so make sure you get everything on your first try.

Red flask #1
Found on the plateau where the first waterfall becomes visible, behind a tree.


Red flask #2
You can get it after the first pulley ride. When you arrive to the other side of the waterfall, go down to a ledge next to it. The flask is at the very end of it.


Red flask #3
After you grab #2, ascend the rocky passage and walk under the waterfall. Check behind the tree on your left.


Red flask #4
Available immediately after arriving at the second pulley destination. Turn right and look down the ledge.


Red flask #5
When you arrive to the third pulley ride, don't hop onto it right away. Turn around and go back in the direction you came from. Jump down to the rock to find a flask.


Red flask #6
After riding the third pulley, walk up the stream and follow the path up. Then turn right and look behind the tree.


Orange flask
Do the fourth and fifth pulley rides. When you arrive at fifth pulley destination, just go forward until you find it.

There are 3 red flasks and 1 orange flask under Nokkpond.

It's impossible to dive into Nokkpond for the second time, so make sure you don't miss anything.

Navigation is somewhat difficult in this level, since it's very dark and doesn't have many distinctive landmarks, it helps that the level is very short and linear (it's essentially a corridor) though. Nokken is also being a bother. Screenshots aren't going to be of great help, so I'll try to describe flask location in relation to other things and health pickups.

Red flask #1
You'll see some health potions in the beginning of the level. Follow along them, and then you'll see Nokken's shining eyes in the distance. Approach it and scare it away with your light flashes. Keep going and you should see Nokkens eyes again, as well as +25 health potion. Jump and look around - hopefully you'll see a red flask somewhere to your right.


Orange flask
Shoo away Nokken for the second time. It's a bit hard to tell where you're supposed to go, it's somewhat in the same direction where Nokken was. Just try to find a way deeper, and eventually you'll drop onto a pipe. There should be a +10 health on your left and emergency health potion on your right. Go right and follow the pipe - it will lead you to an orange flask. This is where drowned zombies become a real nuisance so watch out for them. Flash them if they grab onto you.


Red flask #2
After you grab the orange flask, turn around and follow the pipe in other direction. The pipe will eventually turn left. At this point Nokken will actively try to go after you, so keep your situational awareness. Follow the pipe. You will see two +10 health potions on your sides. The red flask is in this area, just before these potions, on your right.


Red flask #3
Keep following the pipe. After a while it will turn right and go down. Fall all the way down to the bottom of Nokkpond, and you will see some skeletons entangled in nets. Go forward and you will reach your objective - the drowned notesheet. After getting it, proceed in the same direction a bit further - that's where the last flask is.

There are 6 red flasks and 1 orange flask in Sourwood. Additionally, there's a sling upgrade to be found.

Red flask #1
The first red flask is around the starting area of the level. Talk to the flute player and walk across a beam to the other side and keep going. Skip the next beam you see and go forward to another one. Cross over to the statue and check behind it.


Red flask #2
Ride the pulley down to Lyme ravine. When you arrive, follow the stream. You will find another red flask at the end of a side area to your left. Watch out for ticks hiding in the trees!


Sling upgrade
You can find it after clearing the first spider-infested area and going through the cave. Ride the elevator up, then look back and jump to the ledge with +10 health on it. Keep going that way and you'll find a special flaming bag, giving you +50% sling damage.


Red flask #3
Upon exiting the cave that had rolling rocks, start climbing wooden planks on your right that lead to the top of the spire. Carefully drop down behind the spire to find another red flask. You can then leave by dropping down to the sling upgrade area.


Orange flask
Found on top of the spire surrounded by wooden walkways, behind a tree.


Red flask #4
After you clear the second spider-infested area, you will cross a bridge and arrive at a small pillar with a tree. Start descending by going to the rock with a +10 health on it, then jump down to the next platform. After that, turn around and fall down under the rock that had +10 health on it. Keep going down this way and you'll end up on a larger rock with a red flask on it. Don't worry if you missed it, the level loops onto itself and you'll be able to try again.


Red flask #5
When you defeat the Witchlings, you will be able to walk across the rocks to reach a ledge overlooking the boss fight arena. Wooden planks to your left will lead you to a torment screw, don't forget to grab it. Planks to the right will take you forward through a series of cave tunnels. You will encounter the Grand Mother witch in the first one. The second tunnel is full of spiders. This is where the flask is. It's around the middle of the tunnel, in the left wall.


Red flask #6
Ride the pulley to Forest Lookout, go down the slope past the signs and turn left. The flask is behind the furthest tree.

There are 3 red flasks and 1 orange flask in Darkthroat.

You can't revisit this level, so try to get everything in one go.

Red flask #1
The first red flask is in the large cave where whirlpool is visible. You should probably grab a note from the flute player and an air supply first. Then, going forward from the entrance, turn behind a big rock on your right and walk around it.


Red flask #2
Keep going through this large cave. When you reach stairs leading down to the barrier, keep right. At the intersection, go right and around the stone pillar.


Orange flask
After you get an air tank, a mouth piece and destroy the barrier, you can dive into the whirlpool. Keep advancing and you will see a message in a bottle. Go up the path to the left to find an orange flask.


Red flask #3
Go through the tunnel beyond the bottle. Cross the plank leading to a long rock. The third red flask is at the end of this rock.

There are 3 red flasks and 1 orange flask in Marebog.

The situation in this level is somewhat similar to Under Nokkpond. It's dark, with heavy fog, and you're being chased by Mare. Fortunately, features in this level are more distinct so it's a bit easier to figure out where things are.

This level also can't be visited again.

Red flask #1
This one is free for grabs, to the right of the shack, behind a tree.


Red flask #2
Take a nap and get introduced to Mare. Then proceed into the swamp and keep going until you find an obelisk surrounded by rocks. (there's only one way to go so you won't miss it). The flask is behind the obelisk.


Red flask #3
Proceed through the swamp. You will come to a small island with some trees and a torch. Go forward and you will reach next island, which has three ways to go. Go to the right, the flask is at the end of this path.


Orange flask
Keep going through the swamp. Eventually you'll arrive at a place with a torch and pointy rocks, where path turns right. Follow the path alongside pointy rocks and fallen trees, until you see two torches. To the left of the path marked by torches, there's a small black rock. Behind this rock, another path leads to a dead end with an orange flask.

There are 8 red flasks and 1 orange flask in Granite Gash.

Red flask #1
Ride the pulley to the mountain valley, then walk forward a bit and go into the cave passage on your right. When you exit it, turn left and look for the flask.


Red flask #2
After mercilessly massacring some poor bumblebees you can ascend the stone stairs and arrive at a small stone bridge. Cross it and go to the right where emergency health is. From there you can climb up to the rock in front of you (if you are having trouble with it, you can also jump there from above). Proceed along this rock and you'll find a red flask in some foliage.


Red flask #3
Pass through the cave behind a waterfall. The flask is located right after the exit, on your right.


Red flask #4
Escape the flooding cave. Then, you can go to the (locked at the moment) Mountain Tower and search behind it for a red flask.


The part of the level that has flasks #5 and #6 (starting with the catapult and ending with leaving the spider cave) can only be visited once, so make sure you get them both on your first pass.

Red flask #5
You can find it just before the entrance to the spider cave. After jumping over the waterfall, go to the right of a rock in front of you onto a narrow ledge.


Red flask #6
In the spider cave over a floor trap. Make sure to save before entering the cave, so you can easily retry grabbing it in case you somehow miss it. To get it, just run straight at it full speed.


Orange flask
The orange flask is near the start of the cannon trolls valley. Jump to the rocks next to a pile of snow.


Red flask #7
If you survived cannon trolls, you can go and unlock the Mountain Tower shortcut with the key you got from the spiders. There's a red flask inside of it, on the ground floor near the door.


Red flask #8
You can get the last flask right before the level ends. Go right of the steps leading to an aqueduct.

There are 2 red flasks and 1 orange flask in Hypothermia Waste.

Red flask #1
Ride the big bucket. When you arrive, check under it.


Orange flask
Orange flask is located at the halfway landing point.


Red flask #2
Found at your final destination, behind the rock the net is mounted on.

There are 5 red flasks and 1 orange flask in Haunted Glacier.

Red flask #1
You can get it after the fight with ghostly skeletons, in an area with cracked ice.


Red flask #2
After you traverse a narrow walkway swarming with shadow people, you can find another red flask to the left of the climbing rods.


Red flask #3
At some point you will encounter some ghosts over a stream. When you are done with them (or run away, it's actually possible if you go straight for the climbing rods), climb all the way up and you will reach an area with waterfalls and branching paths. A red flask can be found on the right of the entrance to this area.


Orange flask
It's in the flooded chamber with the monster and the music statue. To drain the chamber, break the ice pillar in a cave in the same general area. The flask is near the drain hole.


Red flask #4
There's another red flask in the same area, on the way to the music door. It's hidden in ice and is barely visible on a small ledge near the stream.


Red flask #5
Can be found after going through the skeletal spiders area and opening a music door, stuck in a wall in a small arena with ghostly skeletons.

There are 9 red flasks and 1 orange flask in Drowned Veins.

Another area with poor visibility and difficult navigation.

Red flask #1
It's in the first chamber of the level, with the graves. On the left, behind one of the graves.


Red flask #2
Found during the first diving section. After encountering red rope and following it for a while, you will end up in a large underwater chamber. Follow the rope to a point where it turns around and goes down. At this point, a red flask should already be visible, to your right and down.


Red flask #3
After getting the skull and opening the skull door, dive and follow the red rope. You will arrive in a chamber with a way forward and a way down, with rope going forward. Follow the rope and you will reach another red potion.


Red flask #4
You'll find it in the large underwater cave area during the fourth diving section. It's near the inverted funnel thingie in the floor. Search around before going down through it. The flask is hidden behind some rocks.


Red flask #5
After swimming down the funnel you will arrive at branching paths. Go down the path without the rope to find a red flask.


Red flask #6
When you get potion #5, swim back and follow the red rope path. Eventually you will come to a chamber, where the rope goes in two directions - up and forward. Swim to the path leading up to find the next red potion.


Red flask #7
This flask is located in the final diving section of the level, accessible after opening a bookshelf passage. Follow left wall immediately after diving and look to your right, you should be able to see it very soon.


Orange flask
Dive deep down. Eventually you'll see a red rope again, follow it. At the fork in the tunnel, go left to find an orange potion.


Red flask #8
Keep swimming until you find a skeleton. The flask is gonna be to the left of the skeleton's head.


Red flask #9
The final flask is placed shortly before the end of the level, behind the hydrothermal vent.


This is the point where you can get the ballista weapon. After getting back to solid ground, you'll see some bars marked with bright red blood drop symbols. The ballista is behind those. You can open the bars if you have at least 40 red flasks.


There is no turning back after you jump down the drywell and enter Primordial Abyss, so hopefully you didn't miss anything up to this point.

There is 1 red flask and 1 orange flask in Primordial Abyss.

Red flask #1
You can find the last remaining red flask after the first petworm fight. It's in a large area with lavafall where you fight several dark entities, behind one of the trees.


Orange flask
Can be found in an open area after the second petworm fight. Cross the bridge and take the path leading down.

There is 1 orange flask on Changeling Island.

Orange flask
The orange flask is located right behind the starting hut.