For a dozen years the Cage had held Lord Ith, but as the Pretender Mairsil's power weakened, so did the bars.

Barl's Cage

{3}: Target creature doesn't untap during its controller's next untap step.

Masters Edition III

For a dozen years the cage had held Lord Ith, but as the Pretender Mairsil's power weakened, so did the bars.

Fifth Edition

o3: Target creature does not untap during its controller's next untap phase.

Chronicles Foreign Black Border

Chronicles

The Dark

o3: Target creature does not untap as normal during its controller's next untap phase.

Does not prevent a creature from untapping at other times. It just stops the “normal” untap during the untap step.

Barl’s Cage doesn’t track the creature’s controller. If the affected creature changes controllers before its old controller’s next untap step, this ability will prevent it from being untapped during its new controller’s next untap step.

If the targeted creature is untapped at the time its controller’s next untap step begins, this ability has no effect. It won’t apply at some later time when the targeted creature is tapped.

You may target any creature with this ability. It doesn’t have to be tapped.