
Devil’s in the Details on Tactician
It’s simple: save-scum above average or near perfect rolls for every turn for every character as soon as you enter the room.
Make sure all of the Mind Flayer’s hits are 19 or 20, make sure the Mind Flayer doesn’t die before Commander Zhalk.
90 minutes later you’ll have it. +75xp all characters. My turn counter showed 9 turns remaining.
Don’t forget to loot Commander Zhalk for a nice 2h.
Loot

Or you can, y’know, just use Command (Shadowheart can use it on the first level) and command commander to drop his weapon. Then there’s no need for save/loading, his damage is negligible.
Or if you followed Fracture’s cheese method. Sword would be super useful on tactician mode, as would the xp, no? I assume they will patch out blocking the path the cambions go through with furniture…
There’s no reason to do this on Tactician if you’re trying for the achievement. You can do it on Casual or Balanced.
Doing it on tactician is purely for bragging rights.