Troll mutates are the result of generations of exposure to corrupting alien energies, such as those found near a gate to the Far Realm. The energy is not only corrupting, but debilitating; these trolls have half the Hit Dice of the common troll. The energies to which they are exposed have caused them to mutate, giving many of them odd deformities, externalized organs, and extra limbs. After generations, some of these changes have bred true; nearly all troll mutates have additional eyes and a third arm. Otherwise, the mutates resemble the basic troll stock; thin, loathsome, and a mottled gray-green in color.
Combat: Troll mutates attack with three claws and a bite. The debilitating effect of the forces causing the mutation also weakens these attacks. Should any of these trolls use a weapon, it would attack with only a +4 damage bonus.
Three rounds after a troll mutate takes damage, it begins to regenerate at three hit points per round. If it regenerates more than 20 points of damage, it has a 20% chance to grow a vestigial appendage or organ as well. As with common trolls, fire and acid damage is not regenerated.
Any blow against a mutate with an edged weapon will, on a roll of 20, sever a limb. Severed limbs fight on, scuttling back to rejoin the troll after the battle.
When reduced to 0 or fewer hit points, the mutate is incapacitated but not slain. It continues to regenerate and may start taking actions as soon as it has a positive number of hit points. If immersed in acid or burned while incapacitated the troll mutate is permanently slain.
Habitat/Society: The troll mutates live in a savage tribe ruled by a powerful matriarch, who has psionic powers. They spend much of their time merely surviving, for they share their environment with roving bands of brood gibberlings, gibbering mouthers, and myconid work bands. (The myconids are not particularly dangerous to the trolls, but are eaten with gusto.) Troll mutates are even more cunning than other trolls.
The corrupting influence of the Far Realm is particularly effective because of the trolls' regeneration abilty. Major regeneration is often accompanied by mutation; each time a troll regnerates more than 20 hit points, it has a 20% chance that a vestigial appendage or organ grows on the regenerating spot. Such a growth has a 50% chcne to grow into full function within 24 hours. Otherwise, the appendage or organ just hangs there as a grotesque parody of the real thing (especially if the organ generated was an internal one). After generations of this effect, new trolls are born with a third arm and additonal eyes; these mutations have become the norm.
Troll Regeneration Table
1d12 - Appendage
1 - Arm (claw 1d4+1)
2 - Arm (claw 1d4+1)
3 - Leg
4 - Tail (whip 1d6+3)
5 - Eye
6 - Eye
7 - Tentacle (constrict 1d4+1)
8 - Internal organ
9 - Head (bite 1d8+1)
10 - Wings (Fly 12, E) or pincer (claw 1d3+1)
Ecology: Long ago, trolls found their way into Firestorm Peak, the location of a gate to the Far Realm, during one of the infrequent openings of teh Outer Gates of the mountain. They live by scavenging, preying upon the gibberlings, myconids, and the odd adventurer.
This creature rules the troll mutates with an iron claw. She is a 6+6 Hit Die creature with two heads, giving her an extra bite attack. The second head also gives her a psionic wild talent, 30 PSPs, and a variation of the project force devotion. If she does not use any bite attacks, she can user her psionic attack, in addition to her other attacks. The psionic attack, usable up to three times per day, is triggered with a roll of 16 or less on 1d20 and inflicts 2d6 points plus the target's AC in damage (negative ACs reduce the damage).
The queen has only two arms, but has a fully functional tentacle-like tail that she can whip over her heads to deliver a stunning blow for 1d6+3 points of damage.
She kills all female trolls in the group to ensure her own supremacy, and confiscates all treasure collected by the trolls for her own hoard.
There's really very little difference between a troll mutate and a regular troll. They've still got a claw/claw/bite. They still regenerate, and this regeneration still doesn't protect from fire and acid. They're just weaker and more pathetic. Their deforming regeneration doesn't really have any mechanical function for the ordinary trolls - they'll be dead in 24 hours of the encounter, most likely. I say we add info for three armed, tail-whip and two-headed trolls as variants of the base troll mutate, probably adding a CR +0-+1 bump.
What we could do to differentiate these guys from ordinary trolls? I think some manner of fortification makes sense - they don't have organs that work in nearly the same way as an ordinary creature's, so it's harder to critically hit or sneak attack them.
Light fortification makes sense, I think. We could also leave off rend, as it's not clear that these are as strong as normal trolls. They have fewer hit dice and also smaller claw damage. (Though the example seems to have 3 arms!)
Abilities: based on hp and natural weapon damage, we could argue for Str and Con of 12-13. This seems a little low for their size, so we could compromise with the normal troll and give them 17 or 18 for each, depending on the bonus we want them to have. I'd put Int at 5, just so they're not as smart as normal trolls.
I tried to expand the table to 1d12, like it said. Maybe another internal organ entry? Should we specify that all mutates have at least one mutation from the table? Maybe if one has multiple mutations, it'd be worth a CR bump after some point.
Nice! The nose can go in the last line and the ear can replace one of the eye entries. Do we want to replace the 2nd arm entry? Maybe the head entry could be a minor psi-like/spell-like ability (as for the matriarch) and the bite entry could go with an extra mouth?