Hellfire Hydra

The hellfire hydra ignores the Concealed condition from smoke.

The hellfire hydra has regeneration equal to 5 × the number of heads it has. If a hellfire hydra's body is missing any heads and the remaining stumps haven't been snuffed out, the hydra attempts a DC 42 fortitude save after it regains Hit Points from regeneration. On a success, one non-snuffed stump regrows two heads; on a critical success, two nonsnuffed stumps regrow into two heads each. The hellfire hydra can never grow more than 10 heads. The hellfire hydra's regeneration only fully deactiva

A hellfire hydra has five heads. A creature can attempt to sever one of the hydra's heads by specifically targeting it and dealing damage equal to the head's Hit Points. A head that isn't completely severed returns to full Hit Points at the end of any creature's turn.

A hellfire hydra can regrow a severed head using hellfire regeneration. A creature can prevent this regrowth by dealing damage to the stump with a cold or water effect, snuffing out its flames. Single-target cold or water effects

A hellfire hydra gains an extra reaction per round for each of its heads beyond the first, which it can use only to make Reactive Strikes. It can't use more than 1 reaction on the same triggering action, even if a creature leaves several squares within its reach, and the hydra must use a different head for each Reactive Strike it makes. Whenever one of the hellfire hydra's heads is destroyed, the hydra loses 1 of its extra reactions per round.

10 feet, 9d6 fire damage, DC 38 reflex save

The hellfire hydra slams each of its heads into the ground, where they explode before quickly reforming. The hellfire hydra creates a number of 5-foot bursts within 10 feet equal to its current number of heads. These bursts can't overlap. Each creature in a burst takes 6d6 fire damage (DC 40 reflex save). This counts as a number of attacks equal to the number of heads the hellfire hydra has toward the hydra's multiple attack penalty.