The unending masses of dretches that inhabit the Abyss are petty, wicked, mercurial evil at its most basic. They are the weakest form of tanar'ri save for manes, but don't let this fool you - they are demonic entities with surprisingly potent supernatural powers.
Tanar'ri Physique: while they are far weaker than most other tanar'ri, dretches are considered 'actual' members of the race. Evolved from the chaotic and evil petitioners of the Abyss, dretches are true planar entities, and possess these tanar'ric capabilities:
* Darkness: all tanar'ri have the ability to share the inherent darkness of their very souls with the world at large. This rudimentary power functions at but Poor (4) rank, but basically 'blacks out' the area a dretch currently occupies (it works within Near range).
* Damage Reduction / Cold Attacks: though they are not immune to the effects of cold attacks, tanar'ri are considerably resistant to such. When exposed to any form of cold in its environment, a tanar'ri may reduce its intensity by 2 CS - applying this reduction even before other defenses.
* Damage Reduction / Magic: furthermore, most tanar'ri possess some degree of resistance to magical attacks, whether they come in the form of environmental effects, spells, or even magic items. Dretches possess 1 CS protection against all forms of mystic assault.
* Dimensional Transit: in addition to being able to teleport, tanar'ri can transition themselves between planes of existence. They may do so with Good (10) ability, though on a failed FEAT roll dimensionally transiting tanar'ri may be subject to error, per a failed teleport. *
* Infravision: many of the Abyss' countless layers are dark beyond mortal ken, and have never seen the light (physically or otherwise). As such, all tanar'ri have evolved the ability to see by heat as well as by visible light, and can do so with Good (10) ability.
* Invulnerability to Fire, Electricity, Heat, and Poison: the tanar'ri are hardy creatures - they have to be to survive at all in the endless, horrific wastes of the Abyss. Their forms have evolved over time to give them complete immunity to fire, electricity, heat, and poison.
* Portal Sense: planar beings all, dretches have the ability to perceive the various rifts that dot the planescape of the multiverse. Most of these doorways are invisible to the naked eye, but all dretches can spy them with ease, doing so with Excellent (20) ability.
* Telepathy: almost all tanar'ri are able to communicate directly from mind to mind - a vital skill when so few speak the same tongue. They can usually broadcast and receive thoughts at Typical (6) rank, enough to get their point across when necessary.
* Teleportation: chaotic creatures all, the tanar'ri can bend space itself to their will. All tanar'ri possess the power to teleport with Remarkable (30) ability, and can avoid teleportation's usual side effects while transporting themselves within the same plane of existence. *
Claws: though physically weak, dretches do have several means with which to directly attack the world - should they feel brave enough. The first such weapons are their long, hook-like nails, which they can use to inflict Edged Attack damage in melee.
Emotion Control / Fear: dread creatures of chaos and evil, the vile dretch can instill great fear into those in its vicinity. A dretch may cause others within Very Near distance to quiver in fear with this Good (10) ranked power, an effect which lasts for 1d10 turns.
Fangs: like their claws, dretches are often more than ready to wield these physical weapons against anyone and anything that they see. These needle-like teeth inflict the same damage as a dretch's claws, their Strength rank in Edged Attack damage, but are even more disgusting.
Redolence: once per day, a dretch may emit a cloud of noxious vapors. This horrible gas has the effect of making its targets nauseous, unable to act at all for 1d10 turns (save for moving) due to the retching it causes, unless they pass an Endurance FEAT vs Excellent (20) rank.
Shrinking: dretches do not possess this power in an active fashion, so much as it is an 'always on' situation describing their diminutive stature. They possess this 'power' at Feeble (2) rank, making them about three to four feet tall, and giving them a -1 size factor.
Summoning: once per day, a dretch may attempt to summon forth more of its kind. This power works at Typical (6) rank, and may draw from one to four more dretches into its presence (roll a second FEAT to determine how many arrive, if successful; white is 1 dretch, green is 2, etc.)
Telekinesis: though rather dim-witted and weak-willed, a dretch may impose its desire on objects in its vicinity. It may only do so with Poor (4) ability, but this allows the creatures to move 100 lbs of matter just by thinking about it!
Limitations / Enhancements:
Susceptibility: like all tanar'ri, dretches are weak against the use of cold-wrought iron weapons, as well as holy water and weapons. Their supernatural defenses are ineffective against such assaults, which inflict at least a quarter of a dretch's maximum Health in damage.
Unattractive 3: dretches are horrible, ugly little things. Looking squat and gaunt, the malformed monsters constantly ooze from the mouth and are covered in unsightly varicose veins. This makes them suffer a -6 CS to reaction rolls, not that they usually care really.
Dretches are dim-witted, petty and wicked. Evil to the core and chaotic in behavior, the dretch either strives to improve its lot by becoming more useful or becoming more powerful, and often abuses manes 'below' it in order to avoid contemplating its own, sorry state of existence.
Dretches are short, squat and gaunt. They possess rubbery, almost hairless bodies that range from white to beige in color, with hints of blue here and there thanks to the eerie, varicose veins that visibly throb beneath it. Dretches have only sparse hair on their bodies.
Their mouths are always slack, with drool issuing forth constantly, and their eyes slope upwards. Furthermore, their noses are flat, having an almost squashed look to them, and their long, pointy ears lay limp alongside their malformed heads. They possess claws and fangs to fight with.
The dretch is the first 'actual' form a tanar'ri takes. Some consider the manes to hold this position, but the tanar'ri do not; while they treat manes and dretches equally poorly, the chaotic fiends at least consider the lowly dretch one of their own (for all the good it does them).
Typically a dretch will come into being when a manes shows some spark of awareness, and it will finally grow from petitioner to tanar'ri. Alternately, they may be the result of a larvae being changed into this form directly on the Mountain of Woe, if they showed great promise.
Finally, dretches sometimes 'just happen'. Instead of manifesting in the Abyss in the form of a larvae or a manes, astoundingly wicked mortals of a chaotic and evil bent may arrive on the plane in the form of a dretch instead. In a mad plane like the Abyss, this happens rather often.
* Depending on which version of the Planescape lore you wish to use, dretches (along with the rest of the tanar'ri) may not have access to these powers any longer, having lost them due to yugoloth meddling. Their presence is at the discretion of the individual Judge.