Creature — Imp 1/1, 3B (4)
Common
{T}: Untap target blue creature.
{T}: Choose target non-Wall creature the active player has controlled continuously since the beginning of the turn. That creature attacks this turn if able. If it doesn't, destroy it at the beginning of the next end step. Activate this ability only before attackers are declared.
Illus. Mike Raabe

10/4/2004: The creature is destroyed if it does not attack because it simply can't do so legally.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Commander