| Name | Edition | Colour | Type | Cost | Power | Rarity | $ |
|---|---|---|---|---|---|---|---|
| Once More with Feeling | UG | White | Sorcery | WWWW | Rare | 1.11 | |
| Ondu Cleric | ZE | White | Creature - Kor Cleric Ally | 1W | (1/1) | Common | 0.18 |
| Ondu Giant | RE | Green | Creature - Giant Druid | 3G | 2/4 | Common | 0.12 |
| One Dozen Eyes | MI | Green | Sorcery | 5G | Uncommon | 0.25 | |
| One with Nature | SC | Green | Enchant Creature | G | Uncommon | 0.30 | |
| One with Nothing | SK | Black | Instant | B | Rare | 0.77 | |
| One-Eyed Scarecrow | IS | Unknown | Artifact Creature - Scarecrow | 3 | 2/3 | Common | |
| Oni of Wild Places | SK | Red | Creature - Demon Spirit | 5R | 6/5 | Uncommon | 0.25 |
| Oni of Wild Places | CM | Red | Creature - Demon Spirit | 5R | 6/5 | Uncommon | 0.24 |
| Oni Possession | CK | Black | Enchant Creature | 2B | Uncommon | 0.25 | |
| Oni Possession | DDDD | Black | Enchantment - Aura | 2B | Uncommon | 0.01 | |
| Only Blood Ends Your Nightmares (Scheme) | AE | Unknown | Scheme | Common | |||
| Onslaught | EX | Red | Enchantment | R | Common | 0.14 | |
| Onulet | RV | Artifact | Artifact Creature | 3 | 2/2 | Rare | 0.52 |
| Onulet | AQ | Artifact | Artifact Creature | 3 | 2/2 | Uncommon | 0.82 |
| Onulet | 4E | Artifact | Artifact Creature | 3 | 2/2 | Rare | 0.51 |
| Onyx Goblet | SA | Black | Artifact | 2B | Common | 0.14 | |
| Onyx Mage | M12 | Black | Creature - Human Wizard | 1B | 2/1 | Uncommon | |
| Onyx Talisman | IA | Artifact | Artifact | 2 | Uncommon | 0.22 |