Thokk doesn't get angrier when you hurt him. He gets angrier when more of you get involved. Every fresh face that lands a hit banks him another stack of Warband Fury - and when the whole party has taken a swing, the coast answers back.
A permanent Fury stack (+1 attack, +2 damage), capped at 4. No prior resource in this bestiary counts UNIQUE attackers rather than raw damage or misses.
A scripted bonus-damage hit on the nearest enemy, on top of his normal attack - just to sell the unstoppable-bull read on sight.
His epic spell detonates in a 10m burst centred on himself, and the stack count (and the list of who's hit him) resets so the next surge starts clean.
Goblin Coast's real ceiling was Malbrek Dredge at CR11 (round 6); Thokk is pitched one notch above at CR12, into 2 of the coast's remaining Sparky slots (a fresh area_audit.py this round found it at 14/16, not the 16/16 "full" state round 8 left it in - two slots opened back up).
He is the bestiary's first Minotaur and first Frenzied Berserker - cloned from the module's existing red_minotaur chassis (Race 13) rather than a humanoid donor, so his base Cleave/Great Fortitude/Power Attack/Weapon Specialization (Great Axe) feats are the real racial baseline, unioned with his own new feats rather than overwritten.
Real Epic Spell: Hellball (id 636/876) - granted the same technique as every epic-spell boss since round 1, and its capstone is the literal payoff of Warband Fury maxing out rather than a scheduled autocast.