Bone Warlock

Bone Warlock is a Rift Guardian, a greatly empowered Skeletal Summoner. He can only be encountered as a random boss in a Nephalem Rift.

In combat, it gains following abilities:

In addition, his Arcane Bolt missiles can be shot in three modes: Countess Julia's Cameo amulet can make the fight a lot easier, but overall, it is a simple boss, provided players have area of effect skills to dispatch skeletons.
 * Wormhole affix with greatly increased damage.
 * Summoning: can summon random three out of four types of minions, conjuring a squad of skeletons of the same type (3-5 at a time) once every 15 seconds. Each type of Skeletons has a special ability, and while at least one skeleton of that type is alive, Bone Warlock gains an additional ability.
 * Quick Bones: Fast; Bone Warlock gains Teleporter.
 * Reflecting Bones: Reflects Damage; Bone Walock gains Reflects Damage. Can apply to other minions as well.
 * Mortar Bones: Mortar; Bone Warlock gains Quad Shot (see below).
 * Knockback Bones: Knockback; Bone Warlock gains Knockback.
 * Charged Shot: the missile is very slow, but its damage is augmented to insane.
 * Triple Shot: the missiles fly faster, but their damage is weaker, three at a time. The angle is very sharp, though, and at close distance a character can easily be hit by all three at a time (resulting in very heavy Arcane damage).
 * Quad Shot (with Mortar Bones minions only): same as Triple Shot, but hits harder and shoots four missiles rather than three.