A named threat of Aventhine Sewers, 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.
A ranged bolt of acid that leaves a permanent curse ticking on whoever it lands on - and a running tally in her own memory of exactly how much.
A cloud of biting rot rolls outward, sapping strength from anyone caught in it.
Her one granted Epic Spell, sized to every Blight she's banked all fight, then a haste and regeneration that never turns back off.
CR 10 is set against Aventhine Sewers's own real ambient ceiling, not auto-computed from level alone - a genuine Warlock 10 build at 10 total levels.
Hit points (60) 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 Sable Korrin is ever up in Aventhine Sewers at a time.