A named threat of The Outer Tunnels, encountered rarely and never in numbers - real Dungeons & Dragons statistics, no auto-computed shortcuts.
Layered on top of the module's own combat AI, which still picks targets and positioning. The fight below moves through real hit-point-gated phases; every save DC and attack bonus computes from the stat block above at runtime.
She strips a buff clean off a target - haste, an AC ward, whatever it is - and wears her own version of it instead, never the exact copy.
The more she's taken this fight, the harder the payoff lands.
Nothing she steals returns to its owner.
CR 11 is set against The Outer Tunnels's own real ambient ceiling, not auto-computed from level alone - a genuine Vermin 11 build at 11 total levels.
Hit points (105) follow this project's own average-hit-dice convention, and every save/attack bonus derives from the ability scores above at runtime - nothing here is hardcoded past the phase gates themselves.
Boss-flagged (bypasses the drop-rate roll, two loot-generation passes) and gated to a single spawn - only one Zhress is ever up in The Outer Tunnels at a time.