Mindslayer Unlock Guide

Roll Yeek Archmage, build Tribeam (one point in the first lightning skill, four points in the first fight skill, three points in the second Arcane skill - it gives you a rolling machinegun of line AOE nukes to drop every round), put only as many points into Mag as you need to unlock skills and dump everything else into Con (Yeek Archmages gain like 2HP per level and some of the more dangerous basic enemies can put you down in one crit if you don't invest heavily in Con), get Phase Door to 4 in the Conveyance tree.

Do the two Mandatory Yeek dungeons, step into the Halfling Complex, pop your Rod of Recall. Clear all the T1s and T2s, get to like 15-20, then head back down to the Halfling Complex basement. Open the door, cast Phase Door on the Yeek Wayist and toss him as far back as you can, then tribeam Subject Z to death.

This also works well for getting Yeek in the first place, just roll Archmage as anything besides Yeek.