The Mark XXI Armor (codenamed Midas) was Tony Stark's twenty-first Iron Man suit that was specialized for supersonic flight. It was a part of the Iron Legion. It was destroyed by the Clean Slate Protocol activated by Tony Stark.
The Midas Armor was called, along with the rest of the Iron Legion, to help Tony Stark and James Rhodes during their fight against Aldrich Killian and his Extremis Soldiers. During the course of the fight a number of armors were destroyed, though they eventually managed to eliminate all of the Extremis Soldiers. At the end of the battle the remaining suits that were not destroyed by Extremis Soldiers were destroyed when Stark activated the Clean Slate Protocol, including the Mark XXI. 
Like the Mark XIX, the Mark XXI can fly at supersonic speeds. It has the potential to make a sonic boom, but might fall apart if attempted. This is why Stark made the Mark XL, which can go at hyper-velocity speeds without falling apart.
- This suit's name is a reference to a popular character in Greek mythology called King Midas for his ability to turn everything he touched with his hand into gold.
| Mark I • Mark II • Mark III • Mark IV • Mark V • Mark VI • Mark VII|
Mark VIII • Mark IX • Mark X • Mark XI • Mark XII • Mark XIII • Mark XIV • Mark XV • Mark XVI • Mark XVII •
Mark XVIII • Mark XIX • Mark XX • Mark XXI • Mark XXII • Mark XXIII • Mark XXIV • Mark XXV • Mark XXVI •
Mark XXVII • Mark XXVIII • Mark XXIX • Mark XXX • Mark XXXI • Mark XXXII • Mark XXXIII • Mark XXXIV •
Mark XXXV • Mark XXXVI • Mark XXXVII • Mark XXXVIII • Mark XXXIX • Mark XL • Mark XLI
Mark XLII • Mark XLIII • Mark XLIV/Veronica • Mark XLV • Mark XLVI • Mark XLVII • Mark XLVIII • Mark L • Mark LXXXV
|Mark I • Mark II/Iron Patriot • Mark III • Mark IV • Mark V • Mark VI • Mark VII|
|Mark I • Mark II|
|Spider-Man Suit • Iron Spider Armor|
|Iron Man Armor: Mark XLIX|