| Master of Cruelties (2 variants) | 1565 |
| Master of the Feast | 7106 |
| Master of the Wild Hunt (2 variants) | 1249 |
| Master of Waves (2 variants) | 1278 |
| Masterwork of Ingenuity | 863 |
| Matter Reshaper (2 variants) | 1048 |
| Max, the Daredevil (2 variants) | 345 |
| Maximus, Knight Apparent (2 variants) | 2449 |
| Mayael's Aria | 1848 |
| Mayhem Devil (2 variants) | 1715 |
| Maze's End | 1834 |
| Mazirek, Kraul Death Priest (2 variants) | 1418 |
| Mazirek, Kraul Death Priest (2 variants) | 1766 |
| Meandering Towershell (2 variants) | 236 |
| Mechanized Production | 1841 |
| Mechtitan // Mechtitan (2 variants) | 1969 |
| Mechtitan Core // Mechtitan Core (2 variants) | 1965 |
| Megantic Sliver | 651 |
| Meltdown (2 variants) | 2296 |
| Memnarch (2 variants) | 1626 |
| Memory Lapse | 2142 |
| Mental Misstep (2 variants) | 1179 |
| Mental Misstep (2 variants) | 2373 |
| Mental Note | 2154 |
| Merciless Executioner (2 variants) | 1025 |
| Meren of Clan Nel Toth | 52 |
| Merfolk of the Pearl Trident | 714 |
| Mesa Enchantress (2 variants) | 282 |
| Mesmeric Orb (2 variants) | 2457 |
| Mesmeric Sliver | 620 |
| Metallic Mimic (2 variants) | 194 |
| Metalwork Colossus (2 variants) | 377 |
| Metalwork Colossus (2 variants) | 378 |
| Metamorphose | 2155 |
| Meteor Golem (2 variants) | 1660 |
| Meteor Golem (2 variants) | 2225 |
| Meteor Golem (2 variants) | 285 |
| Michiko Konda, Truth Seeker (2 variants) | 259 |
| Michonne, Ruthless Survivor | 146 |
| Midnight Clock (2 variants) | 2217 |
| Midnight Reaper (2 variants) | 1171 |
| Might Sliver | 652 |
| Miirym, Sentinel Wyrm (2 variants) | 2500 |
| Mikaeus, the Unhallowed (2 variants) | 490 |
| Mikaeus, the Unhallowed | 846 |
| Mike, the Dungeon Master (2 variants) | 346 |
| Miles "Tails" Prower (2 variants) | 2085 |
| Mina and Denn, Wildborn | 1270 |
| Mind Flayer, the Shadow (2 variants) | 340 |
| Mind's Dilation (2 variants) | 1180 |