Nikya of the Old Ways

Commander is the only format where Nikya of the Old Ways is worth building around — a five-mana 4/4 with this kind of restriction needs a 99-card deck engineered to exploit her, and the singleton format gives you the redundancy to go full creature-spell mode without gutting your gameplan. In Legacy, Modern, and Pioneer she's legal but effectively unplayed; the noncreature lockout is devastating in sixty-card formats where interaction, cantrips, and removal are load-bearing, and a five-mana creature that does nothing the turn it enters rarely survives long enough to matter. Oathbreaker is the one other shell worth a mention — as a signature spell she's off the table, but as a creature in a green Oathbreaker pile she can generate the same explosive mana if the deck is built correctly.