When this creature enters, put a +1/+1 counter on target creature you don't control.
, : Destroy target creature with a counter on it.

Return target creature to its owner's hand.

Room abilities of dungeons you own trigger an additional time.

: Add .
: Add one mana of any color. Spend this mana only to cast an Ally spell.
, , Sacrifice this land: Return target Ally you control to its owner's hand.

At the beginning of your upkeep, sacrifice this creature unless you discard a card.
, Exile a creature card from your graveyard: This creature deals 4 damage to any target.
: Regenerate this creature.

Return target creature and target land to their owners' hands.

First strike, protection from loose lips (Nothing with an open mouth in its artwork can block, target, deal damage to, or attach to this creature.)

Counter target spell unless its controller pays for each card in your graveyard.

Whenever a nontoken creature an opponent controls dies, put a +1/+1 counter on each creature you control.

Counter target spell. Create a Mutagen token. (It's an artifact with ", , Sacrifice this token: Put a +1/+1 counter on target creature. Activate only as a sorcery.")

Flash
Enchant creature
Enchanted creature is a Turtle with base power and toughness 0/1. It can't attack and loses all abilities. (It also loses all other creature types.)

Whenever this creature attacks, you may pay . If you do, it gains flying until end of turn.

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Protection from Beasts
Morph (You may cast this card face down as a 2/2 creature for . Turn it face up any time for its morph cost.)

Incandescent Aria deals 3 damage to each nontoken creature.

: Gain control of target creature an opponent controls until end of turn. Untap that creature. It gains haste until end of turn. Activate only as a sorcery.

Target permanent becomes an artifact in addition to its other types until end of turn.
Draw a card.

At the beginning of each opponent's upkeep, you manifest the top card of that player's library. (Put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)
Whenever a creature you control but don't own dies, its owner loses 2 life and you gain 2 life.