Wan Shi Tong, Librarian I'm confident that Wan Shi Tong, Librarian will become a Commander staple
Rakdos, the Showstopper Rakdos, the Showstopper can lock out many decks from operating at their best, especially if they dont run imps, demons, or devils
There isn't any good direct comparison to Mangara's abilities, but the closest thing that popped into my head is Runic Armasaur, another creature whose card drawing ability is entirely dependent on your opponents' actions, making the card inconsistent where it sometimes draws you zero cards and sometimes floods you with card draw
Gorma, the Gullet Gorma, the Gullet is an ever-growing Golgari commander that benefits greatly from sacrifice strategies
When a planeswalker is on the battlefield, an opponent can choose which creatures they want to send at the opponent's life total (going face) and which, if any, they want to divert towards the walker
Is Exile into Darkness legal to play