Osyluths speak Infernal, Celestial, and Draconic.

Combat

Spell-Like Abilities: At will-animate dead, charm person, dimensional anchor, doom, fly, invisibility (self only), major image, suggestion, and wall of ice. These abilities are as the spells cast by a 7th-level sorcerer (save DC 12 + spell level).
An osyluth can also teleport without error (self plus 50 pounds of objects only) at will as the spell cast by a 12th-level sorcerer.

Fear Aura (Su): Osyluths can radiate a 5-foot-radius fear aura as a free action. Affected creatures must succeed at a Will save (DC 14) or be affected as though by a fear spell cast by a 7th-level sorcerer. A creature that successfully saves cannot be affected again by the same osyluth's aura for one day. Other baatezu are immune to the aura.

Poison (Ex): Sting, Fortitude save (DC 14); initial damage 1d6 temporary Strength, secondary damage 2d6 temporary Strength.

Summon Baatezu (Sp): Once per day an osyluth can attempt to summon 2d10 lemures with a 50% chance of success, or another osyluth with a 35% chance of success. This is much as though casting a summon monster spell. Summoned creatures automatically return whence they came after 1 hour. A baatezu that has just been summoned cannot use its own summon ability for 1 hour.

Know Alignment (Su): Osyluths always know the alignment of any creature they look upon.

Immunities (Ex): Baatezu are immune to fire and poison.

Resistances (Ex): Baatezu have cold and acid resistance 20.

See in Darkness (Su): All devils can see perfectly in darkness of any kind, even that created by deeper darkness spells.

Telepathy (Su): Baatezu can communicate telepathically with any creature within 100 feet that has a language.