Dark Mage

The Dark Mage is a mini-boss that spawns in the Old One's Army event during wave 5 in Tier 1 and during waves 4 and 6 in Tier 3. It will freely float a bit above the ground. It randomly chooses between three attacks:
 * The Dark Mage summons magical energy, and hurls it directly at the player, dealing high amounts of damage.
 * The Dark Mage summons a large rune, which then generates a large area of light that heals hostile NPCs in its range. This attack also appears to heal the Eternia Crystal. This has not been tested in tier 3.
 * The Dark Mage begins chanting, and areas of purple energy will appear. After a short moment, Old One's Skeletons will appear from them. This attack cannot be done if there are more than 90 enemies in the world.

Trivia

 * The pet drops from the Dark Mage in T1 are one of the highest drop chances for any pet items from enemies, beaten out only by the Bone Key from the Dungeon Guardian.

History
Mage noir 黑暗魔法师