You may choose not to untap Amber Prison during your untap step.
{4}, {T}: Tap target artifact, creature, or land. As long as Amber Prison is tapped, that permanent doesn't untap during its controller's untap step.

• Number: 272
• Rarity: R
• Type: Artifact
• Mana cost: 4
• Color: Artifact
• Artist: Donato Giancola