Nightmare

Card Name

Nightmare

Mana Cost

5

Type

Creature – Nightmare Horse

Rarity

Rare

rules Text

FlyingNightmare's power and toughness are each equal to the number of swamps you control.

Flavor Text

The thunder of its hooves beats dreams into despair.

Legal Formats

Commander, Legacy, Modern, Pioneer, Vintage

Not Legal Formats

Alchemy, Brawl, Explorer, Historic, Pauper, Standard

Rulings

(4/1/2008)
If you control 0 swamps, then the Nightmare has 0 toughness and will be put into its owner's graveyard as a state-based action right before the next player gains priority.
(10/1/2009)
Nightmare's power and toughness changes as the number of Swamps you control changes.
(7/1/2013)
The ability that defines Nightmare's power and toughness works everywhere, not just on the battlefield.
(7/1/2013)
Nightmare's ability counts all lands you control with the subtype Swamp, not just ones named Swamp.