As my steam achievement shows 0.1% of the players got lvl 20 on summoner, so clearly some people need some help.

When you 1st choose the summoner, you can choose 1 of 3 starting passives - green man, green blob, and SNAAAAKe...
Let me tell you what they do.
They summon a minion at the start of the fight.

Green man - is a tank.
Blob is AoE damage thing, and
Snake is 1-2 target damage thing.

The most safe pick is obviously a tank.
You will have all 3 (+Fey) in you starting deck, but when they die - card is gone for the duration of combat, so "Sacrifice" cards are of limited value.

How to play safe as a summoner - easy - you start with a tank, you never ever level him up (not worth it), you put barrier on yourself at 1st opportunity, and everything else is optional.

Main gimmick of summoner - is summons (duh). You can have 4 of them at the time, when they take damage, you take damage, based on their level (that's why high level golem can kill you very very fast), and you can level them up infinitely.

Summons don't do anything, if you don't tell them to, but each turn you have one 0 cost command, that you can use, to activate one.
Summoner himself (Herself if you chose so), have almost 0 options to attack directly, so your damage, might and everything else is mostly irrelevant. Yes you can have 1 attack per battle by quest card, and there is 1 card I saw, that lets you to smack every enemy for 1 sacrifice, but in my opinion it is not worth if (because of limited number of summons).

Summoner ultimate lets you level any one minion 1 time in a turn, for 5 points - 1 lvl, 7 - 2, and 9 - 3.
You get 1 charge per activation of minion per round, and as you get 0 cost activation every turn, I recommend using it even if is 1st turn, you have no other options, and your golem is at 100% hp. You still get a charge for "free".




Now lets look at the summoned options more closely.

Green Man - Tanky boy (Golem?). Tanky boy automatically redirects all the damage to your team on himself, no matter how big damage it is.
If you are under a AoE attack, tanky boy will get full damage of each target, (so it will be 2 minimum - you and tank boy, 5 maximum - with 4 summons). If this attack kills him, he still takes all damage, hitting your hp for measilly his lvl n hp x number of hits.
If you will summon one more - the one summoned first, will still take all hits, until he dies.
Starting hp of the tanky boy is 70 (I think), and if you level him up it will go up by 10 (don't).
If tank boy survives the attack, he will hit the enemy back for 50% damage he took (barrier damage does not count), and this will not go up if you level him up.
As an activation option, tanky boy heals 14 hp + 1 hp per his level. This is negligible without perc, and his retaliate damage will still be 50% of damage he took. Meanwhile as you go farther and farther into the game, the more hits per turn you will face, so if you will have let's say lvl 10 golem, you will take 10 damage with each hit, and he will have 160 hp and healing of 24.
So my opinion is - keep at least one of this boys alive at all times, heal him and save him as possible, but keep his level as low as possible.

Blob thing - Aoe damage. Your go-to if you are facing 4-5 enemies, otherwise wyrm is better.

Wyrm (Snaaake). - your own mini barbarian. With each activation hits 2 times, but random target. Each hit damages armor, making all the following hits hit harder, and on top of that gives marks. 6 marks and you deal double damage for this target this turn (same as the 1st MC class you are allowed to play). With leveling gets stupidly strong stupidly fast. Your go-to damage minion, if you facing 3 or less enemies.
The only bad thing I can say about big boss, is that he is stupid in choosing who to fight. There was one battle, where I fought spirit summoner, and my wyrm kept hitting immortal spirits, and not the main summoner. I won in the end, but with 4 immortal spirits and 1 summoner on the other side, chance of hitting right target was 20%, so keep that in mind.

Both damage minions get +might with each level, and a pitiful amounts of hp. Don't summon one, if you don't have tanky boy, because you have limited number of summons per battle (1 per card owned).

Fey. The minion, that costs 1 to summon, does 0 damage, but with some bells and whistles can be almost useful.
Fey gives 1 charge of ultimate per activation per his lvl, so it is 2 on lvl 1, and 9 on level 8+.
By using ultimate on fey, and activating it, you relatively quickly get recursive system of possible +3 lvl ultimate each turn, that you have free activation.
Oh and he gives all enemy -10% damage, while alive, but who cares. Better than nothing, but don't make this guy a priority.


(Edit №1)
Several commenters say that dead summoned minions can be summoned again. I, myself did not test it recently (because I am stuck on archer run, and refuse to continue it, until devs fix multishot), but I definitely saw the my summon cards in the red pile of (gone for the battle) (bottom right corner of the screen - there are 2 separate card piles). Maybe my one and only run of summoner did not put me into position to test this (I picked all cards possible with leveling), but still, more than one person said it, so It can hold some truth to it.
Text on card says nothing for this problem, and with sheer ammount of bugged mechaniks I encountered, I can't say that anything in this game "works as intended" with any certancy.



We are done with summons (as far as I know), so lets get to the good stuff.

They are risk/reward mechanic of the summoner, and are really good.
Every sigil is 1 use per battle per card, if you can duplicate them they are bonkers, and I did not see one bad sigil yet.
Yes even +50% might one, which you start with. It is 5 lvls worth of damage increase on damage summons, for 1 energy.

Sigils, I saw so far.
+ 50% might 1 energy - use on anyone, except Fey - even golem is "good".

Self awareness - +1 level each turn. Don't use on your golem and you golden.

Self-Recovery - heals 50% of missing hp each turn - put it on your tank.

+10 barrier each turn - put it on your tank.

+50 max hp and some healing on top of than. - put it on your low level tank.

Auto-Activation on turn start - utterly broken on any minion, in my opinion best used on dps one (with self awareness lol). If you can duplicate it and let this minion live - you are golden. On top of every other benefit - each activation charges your ultimate.
Oh, and this card costs 1 energy. Utterly, utterly broken, use it before devs fix it.

Remember that you can use sigils only 1 time per battle per card, and they are wasted if minnion, you used them on dies - and you are golden.

Read what the card says, and use appropriately. Anything with sacrifice is meh (in my opinion).

+5 hp after battle if you don't have 100% barrier uptime yet.
Damage enemy each turn - if you do.
-5 armor for enemy per turn each turn is good.

Anything with armor / might / damage is useless on summoner. (armor is better than nothing if you have nothing else)

-1 energy cost on golem activation is nice. (gives reason to activate golem and allow 5+ card chains)

Auto activation on summoning is great
Your automatic 1st minion count for that, so with golem you get -1 energy cost on random card (if you took golem perc) and 1 ultimate charge on the 1st turn for free.

Auto barrier on battle start (easy flawless every time, if you have auto golem)

Auto leveling for minion, if only one minion active (good if you started with anything than golem, but high level golem can kill you super fast, so be aware)

Hurp-Durp better-faster-something-stronger minions - fine.

Does this one thing, but once or for 1 (2) turns. - Meeeh. Better plan to live more than one turn, in my opinion.

Hope this guide helped.