Theater of Horrors is a rare Enchantment card from Duskmourn: House of Horror Commander (DSC), collector number 236. Current market price: $0.34, TCGplayer market prices via Scryfall.
At the beginning of your upkeep, exile the top card of your library. During your turn, if an opponent lost life this turn, you may play lands and cast spells from among cards exiled with this enchantment. {3}{R}: This enchantment deals 1 damage to target opponent or planeswalker.