You may have Auton Soldier enter the battlefield as a copy of any creature on the battlefield, except it isn't legendary, is an artifact in addition to its other types, and has myriad. (Whenever it attacks, for each opponent other than defending player, you may put a token that's a copy of this creature onto the battlefield tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

Draw three cards, then put two cards from your hand on top of your library in any order.

Commander creatures you own have "When this creature enters or leaves the battlefield, draw a card."

Counter target noncreature spell. Its controller loses 2 life.

{3}, {T} or {U}, {T}: Return target creature to its owner's hand unless its controller pays {1}.

Exile up to two target creatures you control, then return those cards to the battlefield under their owner's control.

Exile two target artifacts, creatures, and/or lands you control, then return those cards to the battlefield under your control.

Gudul Lurker can't be blocked.

Megamorph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)

Whenever Identity Thief attacks, you may exile another target nontoken creature. If you do, Identity Thief becomes a copy of that creature until end of turn. Return the exiled card to the battlefield under its owner's control at the beginning of the next end step.

Destroy target creature. You lose 2 life.

Create a token that's a copy of target creature you control, except the token has flying and it isn't legendary.

Menace

When Massacre Girl enters the battlefield, each other creature gets -1/-1 until end of turn. Whenever a creature dies this turn, each creature other than Massacre Girl gets -1/-1 until end of turn.

Surveil 3. (Look at the top three cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Take an extra turn after this one. Exile Part the Waterveil.

Awaken 6--{6}{U}{U}{U} (If you cast this spell for {6}{U}{U}{U}, also put six +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

At the beginning of your upkeep, you draw a card and you lose 1 life.

{1}, {T}: Return target creature you control and each Aura attached to it to their owners' hands. Activate only during your turn.

Create a token that's a copy of target creature you control, except it isn't legendary.

Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Deathtouch

Other Assassins you control get +1/+1.

Whenever a player loses the game, if they were attacked this turn by an Assassin you controlled, you win the game.

When Ravenloft Adventurer enters the battlefield, you take the initiative.

If a creature an opponent controls would die, instead exile it and put a hit counter on it.

Whenever Ravenloft Adventurer attacks, if you've completed a dungeon, defending player loses 1 life for each card they own in exile with a hit counter on it.

Scry 2, then draw two cards. You lose 2 life.

Target artifact, creature, or land phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

Whenever you activate an ability, if it isn't a mana ability, you may pay {2}. If you do, copy that ability. You may choose new targets for the copy.

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.

Put a +1/+1 counter on target creature. It phases out. (Treat it and anything attached to it as though they don't exist until its controller's next turn.)

Equipped creature gets +1/+1 and has haste.

Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

When Tribute Mage enters the battlefield, you may search your library for an artifact card with mana value 2, reveal that card, put it into your hand, then shuffle.

When Trophy Mage enters the battlefield, you may search your library for an artifact card with mana value 3, reveal it, put it into your hand, then shuffle.

Enchant creature

{U}{U}: Enchanted creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

{U}, {T}: Return target permanent you control to its owner's hand.

Whenever you cast a spell that targets only a single artifact or creature you control, create a token that's a copy of that artifact or creature, except it's not legendary.

{1}, {T}: Untap target artifact.