It requires an Imperial backstory, which is set at character creation. Imperial titles only give you the Dignified focus

A psy ability neurotrainer that unlocks the archotechist tree also works.

My solo colonist DOES NOT have an Imperial backstory, just an Acolyte title, and I unlocked Archotechist just fine. It also happens to be one of my favorites, and the first I maxed (except Neuroquake, which is... not useful... for a solo guy).

Originally posted by Latex Santa:

My solo colonist DOES NOT have an Imperial backstory, just an Acolyte title, and I unlocked Archotechist just fine. It also happens to be one of my favorites, and the first I maxed (except Neuroquake, which is... not useful... for a solo guy).

There are a lot of imperial backstories that don't look like imperial backstories at first glance. You also get a random path unlocked for free (which might (?) overwrite backstory restrictions.)

My random path was Harmonist. Which wasn't a loss, since Harmonist is not bad at all. But I'll be focusing on maxing Warlord now and then getting started on Necropath (minions, life draining, psyfocus restoration in the field via corpse recycling). Maybe Staticlord next, for anti - mech options other than "shoot them / hit them".

Originally posted by Latex Santa:

My random path was Harmonist. Which wasn't a loss, since Harmonist is not bad at all. But I'll be focusing on maxing Warlord now and then getting started on Necropath (minions, life draining, psyfocus restoration in the field via corpse recycling). Maybe Staticlord next, for anti - mech options other than "shoot them / hit them".

Spoilers on the best path to use against mechs:


Frostshaper.
Pros: Snap Freeze stuns anything and everything, from animals to pawns to mechs, in an icecube for a few minutes. One cast is enough to down them from hypothermia, two is enough to kill.

This could be considered a bug, as mechs are normally immune to cold, but the way Rimworld is coded means that there's no cold damage type, and therefore no cold damage resistance.

Utility: Comes with a variant of Wallraise and can create freezers.

Cons: None! You can use this to take prisoners or kill at your leisure. Some of the direct damage abilities even scale with Psychic Sensitivity, which can get quite ridiculous with enough investment.


Staticlords:
Pros: Good against humans, as they deal tons of fire damage, in an AOE, with significant range. Most abilities have very fast cast times, and shut down pawns by setting them on fire.

Utility: Turn batteries into power generators.

Cons: [bold]Useless against mechs.[bold] The EMP stuns mechs for about as well as an EMP grenade, mechs are immune to the burn damage, and the few abilities with explosive damage split their damage with burn, and therefore barely tickle mechs. Against pirates, causes death by a thousand small burns, leading to mass infections when you try to recruit/harvest survivors.


Flamelords
Pros: Nothing shuts down tribals and 100 husky manhunters like setting a massive AOE on fire. Combine with a Wildshapers Brambles for hilarious effect. Fire Shield makes one immune to Inferno Cannons and sets enemy melee attackers on fire.

Utility: A few abilities that put out fires.

Cons: Mechs are completely immune to fire, as are Warlord Psycaster raiders that wear pheonix power armor. When used against pirates, tends to burn up the loot and kill potential prisoners.


Note that I don't even consider combat psycasts to be the strongest. A Protector with Guardian Skip Barrier and a firing squad is devastating, as is a clever Skipmaster, or a Technomancer crafter. It has been argued that Nightstalker+Necropath is the most OP. I haven't tried Harmonist or Empath, but I suspect they are also incredibly strong when used creatively.

Thank you, RedPine, for sharing your findings with us. I'll probably switch my priority to unlocking Frostshaper next instead of Staticlord on my solo superman. I'll mix and match with superpowers of my choice from VFE Ancients (thank you Supersoldiers Unleashed and Ancients Craftable mods), together with the Starseeker class from RimWorld of Magic for maximum devastation.