Phantom

The Phantom is the first boss in Elemental Unleash. It is meant to be fought after Plantera and around the time of Duke Fishron. It is spawned in by using the Paladin Emblem while in the Dungeon.

Appearance
It is a light blue humanoid ghost without any limbs with a knightly attire. Its chest has a yellow Christian Cross on it. Despite lacking arms, it has 2 separate hands.

Movement
It mainly hovers in circles around the player, shooting its hands at the player. It also can shoot projectiles and hammers. It sometimes uses its hands as lasers and rotating it around while firing it. It also launches 5 large circles at the player with a slight delay to help escape. During the fight, the Phantom will summon small blue orbs. These must be defeated or else the Phantom will release a powerful attack. Once defeated he will drop some weapons as well as Phantom Plates which can be used for creating the Elemental Purge which is the Spirit of Purity's summoning item.

Note: Some stuff above is quoted from the mod author's forum post found here.