Troll, Mimic
This is a vaguely troll-like creature; its right arm ends in five sharp blades, its left arm is a blunt mace head and its head is on fire.

Mimic Troll (CR 8; XP 4,800)
CE Large humanoid (giant)
Init +6; Senses darkvision 60 ft., low-light vision, scent; Perception -1
AC 19, touch 11, flat-footed 17
(+2 Dex, +8 natural, -1 size)
hp 112 (9d8+72); fast healing 5
Fort +10, Ref +8, Will +4
Speed 30 ft.
Melee 2 claws +13 (1d6+8), bite +13 (1d8+8)
Space 10 ft.; Reach 10 ft
Special Attacks assimilation, rend (2 claws; 1d6+12)
Str 27, Dex 14, Con 24, Int 6, Wis 8, Cha 8
Base Atk +6; CMB +15; CMD 27
Feats Combat Reflexes, Improved Initiative, Iron Will, Stand Still, Toughness
Skills Perception +7, Survival +7
Languages Common, Giant
Environment hills, mountains
Organization solitary
Treasure standard
Special Attacks
Assimilation (Su) A mimic troll gains special attacks every time it suffers hit point or ability damage from any source, according to the table below. These abilities last one hour before fading away

Damage Type Details
Weapon One natural attack increases by a damage size, treated as magic to bypass DR, gains any weapon special abilities of the attack.
Energy (acid, cold, electrical, fire) One natural attack gains +1d6 energy damage/spell level or +1d6 if no spell level.
Energy (force, sonic, untyped magic) breath weapon (30 ft. cone 1d8 sonic/spell level minimum 2d8; F-DC 21).
Negative energy energy drain (1 level; F-DC 21).
Poison Assimilated Poison (Ex) Bite—injury; save Fort DC 21, frequency 1/round for 6 rounds, effect 1d3 Str, cure 2 consecutive saves.
Other As determined by the GM.

Mimic trolls are true horrors in every sense. Besides their race’s natural strength and toughness, they have the dreadful ability to assimilate the magical powers and effects they are affected with. Thus, a mimic troll affected by fire does not burn, but instead gains a fire attack form; a mimic troll cut in two by a blade not only rejoins its body but also gains a slashing attack, and so on. Mimic trolls like to let their opponents attack first, if only to add to their assimilation repertoire.

On Porphyra
Mimic trolls are likely a by-product of the horrific energies released by the Red Night a thousand years ago, and subsequently haunt the Ghadab and the Mountains of Wrath, sometimes straying into the underworld entrances common in the Minotaur Highlands. They meet to breed once a decade at the Pit of Giants.