Your search for "Unending Nightmare STP6-EN005" revealed the following:
Unending Nightmare - STP6-EN005 - Ultra Rare from Speed Duel Tournament Pack 6, available at 401 Games Canada. Rarity: Ultra Rare Card Text:You can pay 1000 LP, then target 1 face-up Spell/Trap on the field; destroy it. You can only...