| Name | Attribute | Level | Type |
|---|---|---|---|
| Undead Knight | 57 | General Monster | |
| Undead Knight | - | 60 | General Monster |
| Undead Mage Golgoroth | - | 1 | General |
| Undead Mage Golgoroth | 44 | Boss Monster | |
| Undead Maniac | 43 | General Monster | |
| Undead Pirate | 76 | General Monster | |
| Undead Pirate Captain Yamar | 76 | Boss Monster | |
| Undead Prowler | 44 | General Monster | |
| Undead Prowler | - | 5 | General |
| Undead Prowler | - | 1 | General |
| Undead Puppet | 90 | Elite Monster | |
| Undead Puppet | 110 | Elite Monster | |
| Undead Puppet | 110 | Elite Monster | |
| Undead Puppet | 100 | Elite Monster | |
| Undead Puppet | 110 | Elite Monster | |
| Undead Soldier | 85 | General Monster | |
| Undead Soldier | 85 | General Monster | |
| Undead Specter | 80 | Elite Monster | |
| Undead Specter | 70 | Elite Monster | |
| Undead Specter | 80 | Elite Monster | |
| Undead Specter | 90 | Elite Monster | |
| Undead Spirit Warrior | 83 | General Monster | |
| Undead Villager | - | 1 | General |
| Undead Villager | - | 1 | General |
| Undead Villager | - | 1 | General |
| Undead Wanderer | 43 | General | |
| Undead Warrior | 83 | General Monster | |
| Underground Crustdrone | - | 80 | General Monster |
| Underling 1 | - | 1 | General |
| Underling 2 | - | 1 | General |
| Underling 3 | - | 1 | General |
| Undying Ectoplasm | 110 | General Monster | |
| Undying Elegance | 110 | Elite Monster | |
| Undying Elegance | 110 | General Monster | |
| Unexpected Harvest | - | 1 | General |
| Unexpected attack | - | 1 | General |
| Unexplored Places | - | 1 | General |
| Unholy Automaton Rex Machina | - | 20 | World Boss |
| Unholy Automaton Rex Machina | - | 30 | World Boss |
| Unholy Automaton Rex Machina | - | 20 | World Boss |
| Unholy Automaton Rex Machina | - | 90 | World Boss |
| Unholy Flame | - | 64 | Elite Monster |
| Unholy Flame | - | 64 | Elite Monster |
| Unholy Sprite | 55 | General Monster | |
| Unidentified Ghost | - | 1 | General |
| Unidentified Ghost | - | 1 | Interactive |
| Unknown Creature | - | 1 | General |
| Unknown Dimension | - | 1 | General |
| Unknown Dimension | - | 1 | General |
| Unknown Dimension | - | 1 | General |