The chaotic fiends of the Abyss, the tanar'ri are a numberless horde ruled by appetite and rage, locked in eternal war with the baatezu and fond of terrifying their prey before the kill.
Ask in the gambling dens and smoky parlors of the great planar city about the worst place in existence, and every tale ends at the Abyss: endless bleak layers where chaos and despair reign and suffering takes solid form. Others are tormented there. Tanar'ri flourish.
Tanar'ri are fiends of enormous power, as the baatezu are, yet their evil differs. The lawful baatezu pursue calculated doctrine toward dominion over all planes and tempt mortals into intellectual sins like pride and ambition. Tanar'ri are chaotic evil made flesh, driven by insane, violent urges, and lure mortals into vice and crimes of passion. Dim ones attack without thought and fight until slain, while greater and true tanar'ri prowl the Ethereal and Astral planes in an unending search for new prey.
Even the least tanar'ri can use infravision, darkness 15' radius and teleport without error, and each can gate in others as its own entry describes. Greater tanar'ri suffer only half damage from silver. A shared telepathy lets every tanar'ri communicate with any intelligent being regardless of language, and those of Average Intelligence or better can converse. Weapons forged in the Abyss dissolve when their tanar'ri owner dies; one that does not was probably made elsewhere.
From weakest to strongest, there are five ranks. Least: dretch, manes, twisted demon. Lesser: alu demon, charger demon, ape demon, horned demon, cambion, ghoul demon, succubus, rat demon, handmaiden demon. Guardian: warden demon. Greater: babau, buzzing demon, siege demon, shadow demon, sea demon. True: balor, glabrezu, hezrou, marilith, nalfeshnee, rot demon, vrock. The spider-fiends are a separate subrace.
The ranks are just rough gauges of destructive power. Tanar'ri value only strength, so a mighty lesser fiend who defeats a greater one rises in standing, and the scramble for position never ends. Only the warden demon, oddly detached from the hierarchy, stays out of it.
The tanar'ri are one side of the endless war between demons and devils, fighting the baatezu since the dawn of their existence. The baatezu wage war with planning and strategy; the tanar'ri are a disordered horde that wins by attrition and numbers, easily a hundred of them for every baatezu, though counting is hopeless across infinite planes. They fight mostly because the true tanar'ri feel a primal hunger to wipe out baatezu, and they bully weaker fiends into serving that urge.
Most tanar'ri feed on flesh or life force and seem to draw more sustenance from a victim filled with terror. Ordinary predators stalk and kill; tanar'ri stalk, terrify and then kill.
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Related: Alu Demon [Lesser Tanar'ri] · Ape Demon [Lesser Tanar'ri] · Babau [Greater Tanar'ri] · Balor [True Tanar'ri] · Buzzing Demon [Greater Tanar'ri] · Cambion [Lesser Tanar'ri] · Charger Demon [Lesser Tanar'ri] · Dretch [Least Tanar'ri] · Ghoul Demon [Lesser Tanar'ri] · Glabrezu [True Tanar'ri] · Handmaiden Demon [Lesser Tanar'ri] · Hezrou [True Tanar'ri]