Ember

Ember is a Rift Guardian, a greatly empowered Morlu Incinerator and a direct counterpart of Rime. He can only be encountered as a random boss in a Nephalem Rift.

In combat, he gains following abilities:
 * Summon Lunatics: spawns four to six Fallen Lunatics, who explode for high Fire and Physical damage. They have a shorter detonation period, faster movement speed and more Life than normal Lunatics, and leave a Molten trail behind (although on death, they do not release a Molten blast).
 * Summon Shamans: spawns two s with empowered life and damage.
 * Meteor: identical to a normal Morlu Caster, but has larger area of effect, lesser damage over time fire duration, and greater instant damage. Cannot cast two Meteors at the same time. At 50% Life or lower, halves the cooldown of Meteor. Aimed at random player.
 * Teleporter affix (with reduced cooldown).
 * Repulsion: identical to a normal Morlu Caster, but deals significant damage.

Since all of this Rift Guardian's damage is Fire, having a Star of Azkaranth may make the fight very easy, as the boss will be completely unable to hurt the player. Only his suicide minions pose danger in that case.