Lazav, Familiar Stranger

Whenever you commit a crime, put a +1/+1 counter on Lazav. Then you may exile a card from a graveyard. If a creature card was exiled this way, you may have Lazav become a copy of that card until end of turn. This ability triggers only once each turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Chameleon, Master of Disguise

You may have Chameleon enter as a copy of a creature you control, except his name is Chameleon, Master of Disguise.
Mayhem {2}{U} (You may cast this card from your graveyard for {2}{U} if you discarded it this turn. Timing rules still apply.)

Superior Spider-Man

Mind Swap — You may have Superior Spider-Man enter as a copy of any creature card in a graveyard, except his name is Superior Spider-Man and he's a 4/4 Spider Human Hero in addition to his other types. When you do, exile that card.

Doctor Octopus, Master Planner

Other Villains you control get +2/+2.
Your maximum hand size is eight.
At the beginning of your end step, if you have fewer than eight cards in hand, draw cards equal to the difference.

Lazav, Wearer of Faces

Whenever Lazav attacks, exile target card from a graveyard, then investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Whenever you sacrifice a Clue, you may have Lazav become a copy of a creature card exiled with it until end of turn.

Doc Ock, Sinister Scientist

As long as there are eight or more cards in your graveyard, Doc Ock has base power and toughness 8/8.
As long as you control another Villain, Doc Ock has hexproof. (He can't be the target of spells or abilities your opponents control.)

Locke Cole

Deathtouch, lifelink
Whenever Locke Cole deals combat damage to a player, draw a card, then discard a card.

Hades, Sorcerer of Eld

Vigilance
Echo of the Lost — During your turn, you may play cards from your graveyard.
If a card or token would be put into your graveyard from anywhere, exile it instead.

Emet-Selch, Unsundered

Vigilance
Whenever Emet-Selch enters or attacks, draw a card, then discard a card.
At the beginning of your upkeep, if there are fourteen or more cards in your graveyard, you may transform Emet-Selch.