Hidden Horror

Creature - Horror 4/4, 1BB (3)
When Hidden Horror enters the battlefield, sacrifice it unless you discard a creature card.¹
If the presence of evil were obvious, it wouldn't be nearly as dangerous.
Illus. Brom

Gatherer Card Rulings [Nov 2009]

• 4/1/2008: When the ability resolves, you choose whether to sacrifice the creature or perform the other action. If you can’t perform the other action, then you must sacrifice the creature.
• 4/1/2008: If the creature is no longer on the battlefield when the ability resolves, you may still perform the action if you want.

Format Legality	Legal in Vintage, Legacy, Extended Banned in Standard
Printings (4/27)	Tenth Edition (Uncommon) Classic Sixth Edition (Uncommon) Portal Second Age (Rare) Weatherlight (Uncommon)