Base creature values. Events, world settings, difficulty and loot bonuses can change an encounter.

The Brainstealer
Bosstiary · ArchfoeBoss rewardCreature resistance values; world limits may adjust them. Negative values indicate a weakness.
Paralysis · Invisibility
Base chance per roll, not a guaranteed reward. Bonuses, world multipliers and boss participation change the result. Charged items use their own quantities. Container contents also require the container to drop.
Sovereign Sigil · 1 · 100%
platinum coin · 1 · 100%
crystal coin · 1 · 100%
violet gem · 1 · 50%
moonstone · 1 · 50%
ultimate soul essence · 1 · 50%
white gem · 1 · 50%
Brainstealer's tissue · 1 · 6%
Brainstealer's brain · 1 · 5%
Brainstealer's brainwave · 1 · 2.5%
Reserve Reliquary · 1 · 2%
Focus of Charged Spider · 1 · 1%
voidsigil staff · 1 · 0.32%
violet hood · 1 · 0.24%
runebark hood · 1 · 0.225%
Eldritch Fluxbow · 1 · 0.21%
abyssreaper rod · 1 · 0.2%
stagbone grimoire · 1 · 0.19%
gravebone breeches · 1 · 0.18%
beastmorph boots · 1 · 0.18%
deepstone barrier · 1 · 0.18%
the voidforge sceptre · 1 · 0.18%
voidscript ward · 1 · 0.17%
runeforge defender · 1 · 0.16%
vis power gloves · 1 · 0.15%
gildedsigil wand · 1 · 0.14%
voidsigil wand · 1 · 0.13%
gilded void staff · 1 · 0.12%
elder voidsigil staff · 1 · 0.11%
gildedsigil staff · 1 · 0.1%
gilded branch rod · 1 · 0.08%
gildedfang rod · 1 · 0.06%
empowered sanguinis power gloves · 1 · 0.06%
skyline bow · 1 · 0.05%
eldritch crystal · 1 · 0.03%
tenebrae rune bag · 1 · 0.025%