"Classic Sixth Edition", "untap step" (3)
You may choose not to untap Amber Prison during your untap step.
, : Tap target artifact, creature, or land. That permanent doesn't untap during its controller's untap step for as long as Amber Prison remains tapped.
Whenever Lead Golem attacks, it doesn't untap during its controller's next untap step.
Creatures with power 3 or greater don't untap during their controllers' untap steps.
Gatherer works better in the Companion app!
, 
: Tap target artifact, creature, or land. That permanent doesn't untap during its controller's untap step for as long as Amber Prison remains tapped.