You may choose not to untap Amber Prison during your untap step. {4}, {T}: 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.
Near Mint - $0.70
Lightly Played - $0.60
Moderately Played - $0.40
Heavily Played - $0.30
Damaged - $0.20
Near Mint French - $0.70
Lightly Played French - $0.60
Moderately Played French - $0.40
Heavily Played French - $0.30
Damaged French - $0.20