Death Hunter

The Death Hunter is a powerful hostile mob that spawns on the Death Day Event.

Spawning
Death Hunters spawn naturally on the Death Day Event. They will despawn if the player gets too far away from them or if the difficulty is set to Peaceful.

Death Hunters can be spawned using /summon nevermine.DeathHunter.

Drops
Death Hunters have a 100% chance to drop one Immortallis Realmstone on death. This cannot be increased with the Looting enchantment. Since Death Hunters are the only source of the Immortallis Realmstone, it is important to take advantage of the Death Day Event when it occurs.

Death Hunters will also drop about 3 XP orbs at death.

Behavior
Death Hunters have the ability to pick up and throw the player. When the player gets within about 15 blocks of one, the player will be pulled towards it, even if the Death Hunter is on the other side of a wall. Getting too close will result in the player being levitated high above the Death Hunter. Trying to escape may throw the player far, where the player will suffer heavy fall damage (unless the player has a Gravitator), or get attacked by different mobs.

Because of their strong pull, Death Hunters can render the player immobile if the player is inside a small structure.

Trivia

 * Death Hunter's pull can affect the player in Creative mode.

References/Sources
http://adventofascension.gamepedia.com/Death_Hunter