The VOIDRUNNER'S CODEX is coming! Explore new worlds, fight oppressive empires, fend off fearsome aliens, and wield deadly psionics with this comprehensive boxed set expansion for 5E and A5E!
Pit Fiend 21
Rakshasa 7 Gold Dragon 8 - All that glitters...
Lich 20
Gelatinous Cube 12
Owlbear 18 Beholder 20 - nothing else left is protected Product Identity, so definitely the most Uniquely D&D monster on the list.
Black Dragon 11