I dunno how much interest is left, but considering in a span of 3 months basically nothing has been found out about the third ending or route, I feel having a dedicated thread where information can be organised would be a good idea for whoever is left hunting for it.

What is Known so far:

-No steps of the Evil EE are known so far.

-Four Players are not needed, Evil EE can be done with a single person.

Potential Items/objects of Interest to furthering Evil EE:

-Poison Bolt and Explosive Bolt aren't used for any EE steps unlike all the other bolt types. Flash Bolt is also a potential lead, as it is only used for the Perkaholic side EE at the moment.

-Might require one of the Secret Vault weapons in some way.

-Strange Tentacled Skull near Explosive Warden Crossbow Bolt, on a shelf. Default Bo3 asset that commonly has glowing eyes that can be lit, stands out as a strange decoration choice. Possibly interactable in some way? doesnt seem related to Warden Crossbow Bolts or Keeper Hammer however.

-Graffiti in Sewer claims "Jack Fell down and broke his crown". Map has both a Lumberjack enemy that is already killed in a specific spot to unlock the Frost Bolt, and a weapon with a Crown on it(Pack a Punched Keeper Hammer). Possible connection of some kind? Tried killing Lumberjack and other boss zombies near graffiti with weapon to no results.

-Graffiti in Dark Room continues Sewer Graffit, "And Jill came tumbling down after him". Unknown what this could be referencing to if meant as a clue of some kind.

-Clock in Safe Area uses same model as Secret Area's side EE clock. No interaction shooting with all bolts, but still stands out.

-Corpse in Poison Bolt Container holding a Raygun. Notably, Raygun appears to be absent from the Mystery Box. Possibly something can be done with corpse? Tried shooting with Poison Bolt, Explosive Bolt, and Flash Bolt to no avail, as well as hitting it with Pack-a-Punched Keeper Hammer.


Confirmed Red Herrings/Unrelated:

-Knifable Keeper Head in Freezer was confirmed via creator to be an "Optional" step for the Bad EE and not related to the Evil EE.

-Completing all known Side EE and all steps for both Evil EE and Good EE do not seem to be required for the Evil Ending.

-The Remnant Harvester is likely unrelated to the Evil EE as it was added after the map's original release while Evil EE was included from the start, unless steps were changed once it was added.

-Knifeable clocks in Secret Area giving timewarp appears to be solely a reference to a side-easteregg in the original map and not related to the Evil ending.

-Killing The Keeper boss inside the secret area(Audio Log mentions him appearing as a glitch on the original map) does nothing.

-Different Colored Locked doors in Secret area is a reference to the original map, and the EE steps required to open them are unavailable in the Conclusion 2's version.

-Vent in Safe Room despite standing out, is just for decoration and has nothing to do with the EE.

-Pack a Punched m60's name is a reference to the movie House of 1000 Corpses. However author has included this on other maps and is unrelated to the Evil EE (Thanks to Si-Honk for noticing the Reference).

-Sound Cue after the Sebastian Communicator is just to indicate that it is over and has no relevance to the evil EE.

-Cell in Safe Room with Audio coming out of it is unrelated, Author mentioned it was an original spot to put the Remnant but passed as they couldn't get rid of the Audio once door opened, so very unlikely it has anything to do with the Evil EE.

Interesting bits of Info:

-In Announcement Video by Author, describes it as "Once again having two EE paths, but three endings", which might imply its not a full EE route of its own but could be reading too much into this.

-In Dev Stream, mentioned he was happy that 'almost everything' tied into an EE or Quest in some way, which paints even more suspicion over the Explosive and Poison bolts.

-Dev Stream confirms Evil EE can be done by a single person indirectly by mentioning he won't show it as no one found it yet.