Nightmare

At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature.

Wilds of Eldraine Tokens

The Nightmare arises from its lair in the swamps. As the poisoned land spreads, so does the Nightmare's rage and terrifying strength.

30th Anniversary Edition

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.

The thunder of its hooves beats dreams into despair.

The List

Arena Beginner Set

Flying
Nightmare's power and toughness are each equal to the number of Swamps you control.

Ashiok, Wicked Manipulator

If you would pay life while your library has at least that many cards in it, exile that many cards from the top of your library instead.
+1: Look at the top two cards of your library. Exile one of them and put the other into your hand.
−2: Create two 1/1 black Nightmare creature tokens with "At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature."
−7: Target player exiles the top X cards of their library, where X is the total mana value of cards you own in exile.

If you would pay life while your library has at least that many cards in it, exile that many cards from the top of your library instead.
[+1]: Look at the top two cards of your library. Exile one of them and put the other into your hand.
[−2]: Create two 1/1 black Nightmare creature tokens with "At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature."
[−7]: Target player exiles the top X cards of their library, where X is the total mana value of cards you own in exile.