Mage-Ring Responder doesn't untap during your untap step.
{7}: Untap Mage-Ring Responder.
Whenever Mage-Ring Responder attacks, it deals 7 damage to target creature defending player controls.

• Number: 232
• Rarity: R
• Power: 7
• Toughness: 7
• Type: Artifact Creature
• Subtype: Golem
• Mana cost: 7
• Color: Artifact
• Artist: Adam Paquette