A named threat of North Goblin Coast, 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 curse settles on one enemy, chosen and re-chosen through the fight.
A third of whatever lands on him is passed straight on to whoever's currently cursed - the instant it happens, not on his own turn.
A permanent rage answers his own mounting scars.
CR 22 is set against North Goblin Coast's own real ambient ceiling, not auto-computed from level alone - a genuine Barbarian 22 build at 22 total levels.
Hit points (264) 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 Kroth Ironscale is ever up in North Goblin Coast at a time.