Very loosely based upon a pit fiend.
Star Spawn
Huge Aberration, Chaotic Evil
Armor Class 19 (Natural armor)
Hit Points 310 (27d12 + 5)
Speed 40 ft., fly 60 ft., swim 40 ft.
STR 26 (+8) DEX 11 (+0) CON 20 (+5) INT 16 (+3) WIS 19 (+4) CHA 18 (+4)
Saving Throws Dex +6, Con +11, Wis +10
Damage...