Let's start with the fleshmorph!
Fleshmorph (Yelad)
Greater Devil
ARMOR CLASS: 4
MOVEMENT: 9"/18" flying
HTK: 10D8
ATTACKS: 2
DAMAGE: 1-10 (Mace), 1-4 (claws)
MAGIC RESISTANCE: 60%
INTELLIGENCE: Genius
ALIGNMENT: Lawful Evil
SIZE: Large 10 feet tall
Yelad was one of the most renown Fleshmorphs and served as Dispater's favored aid, charged with collecting human slaves for Dispater's palace on the second plane of Hell.
Fleshmorphs are bat-winged creatures with tiny, hairy ears, a bald head, and a flattened mound with two holes for a nose. Fleshmorphs carry a poisoned mace (43 to hit) that causes death within two hours of contact.
They can perform once per turn or melee round: Detect Invisibility, Cause Fear, Produce Flame, Read Magic, Wall of Fire, Polymorph to Human Form, Dispel Magic, Detect Magic, Summon Monsters (50% chance of summoning 1-2 Erinyes).
Originally appeared in Role Aids #716 Deadly Power.
It looks like we've got a 10 HD devil (baatezu). We might look to the 10 HD bone devil as a starting point for abilities...
Str 21, Dex 21, Con 21, Int 14, Wis 14, Cha 14