My take on a berzerker barbarian from 5e making you take exhaustion if you empower their rage.
The Salmon merfolk, a breed of warriors normally unremarkable who under duress and threat of extinction find themselves forced into the hormonal transformation one would see in salmon's rut, bulking up horrifically as their body, solely focused on preserving the specie via reproduction cares not to maintain life support beyond that point.

It is thus not uncommon to see these brutish warriors experience necrosis, rotting alive as they carry out their violent acts to push back the invaders and necessiting constant support from their community to survive their own metabolic breakdown.