Ghost

Ghosts are invisible Charged Creepers found in the Mist in the Dwarven Mines. They deal percentage damage to your health, so

Spawning
Ghosts spawn in large numbers all across The Mist.

Drops
Ghosts drop:

Ghosts also drop 150 Combat XP.

Behavior
Ghosts are hostile to nearby players. They have and move slowly, but deal true percent damage, similar to a skeleton master, but based on distance (farther=less damage).

Ghosts only take damage from melee attacks. Item abilities such as Hyperion's Wither Impact and arrow damage (including Bonemerang damage) do not affect Ghosts. An exception to this rule is the Flower of Truth, who's ability damages them.

They have the appearance of an invisible Charged Creeper, where only the charged part is visible, similar to the Creeper Veil of the Wither Cloak Sword.

Tips

 * The Flower of Truth is very good for keeping a safe distance from Ghosts, while healing damage with life steal enchantments. Swapping to a high-damage weapon such as Giant's Sword will allow one to deal more damage.
 * The Soul Whip can deal heavy damage to large groups of Ghosts while staying out of range of their melee attacks.
 * The Phantom Rod allows players to deal damage from afar and avoid taking hits.
 * A good budget way of killing them is by using any fishing rod to throw them into the air. They will then take a decent amount of fall damage depending on how high they fall.