Narcolepsy

Enchantment — Aura    (CMC:2)

Enchant creature At the beginning of each upkeep, if enchanted creature is untapped, tap it.

"It's so cute when it's sleeping, isn't it? Actually, it's still as abhorrent as ever, but at least it's not trying to kill us."

79 ROE • ENJohann Bodin

™ & © 1993—2010 Wizards of the Coast

Legal in: Modern,Zendikar Block,Legacy,Vintage,Freeform,Prismatic,Tribal Wars Legacy,Singleton 100,Commander

Oracle Text (click to copy):

Narcolepsy {1}{U} Enchantment — Aura Enchant creature At the beginning of each upkeep, if enchanted creature is untapped, tap it.

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6/15/2010
Narcolepsy's triggered ability has an "intervening 'if' clause." That means (1) the ability triggers only if the enchanted creature is untapped as any player's upkeep begins, and (2) the ability does nothing if the enchanted creature is already tapped by the time it resolves.
6/15/2010
Narcolepsy doesn't keep the enchanted creature continually tapped. The creature untaps during its controller's untap step as normal, then is tapped when Narcolepsy's ability resolves during that upkeep. The creature may be tapped in response (for example, if it has an activated ability with  in its cost).

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