Spirit Shackle

Enchant creature
Whenever enchanted creature becomes tapped, put a -0/-2 counter on it.

Masters Edition III

Renaissance

Fourth Edition Foreign Black Border

Fourth Edition

Put a -0/-2 counter on target creature every time it becomes tapped. These counters remain even if Spirit Shackle is removed.

Legends

Put a -0/-2 counter on target creature every time it becomes tapped. Counters remain even if enchantment is removed.

Spirit Shackle's ability triggers only when the enchanted creature changes from untapped to tapped. If Spirit Shackle enters attached to an already tapped creature, it won't do anything (until that creature untaps and becomes tapped again, that is).