Rime

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

In combat, he gains increased damage, as well as following abilities: Both types of Frost circles may not intersect to each other.
 * Teleporter affix with a reduced cooldown.
 * Frost Pools: creates 4 small runic circles on the ground that pulse with fast ticks of Cold damage for roughly 4-8 seconds.
 * Frost Ring: creates a larger runic circle compared to Frost Pool, which deals more damage, but recharges longer. Before it appears, a blue circle on the ground blinks briefly, giving one second to leave the area.
 * Frost Bolt Volley: fires three Frost Bolts at 15-20 degrees angle to each other. each dealing high Cold damage. Only used if there are no players in melee range.
 * Blow: melee attack, deals high Physical damage, only used if nothing else is available.

As Rime mostly has Cold attacks, Talisman of Aranoch makes this Rift Guardian much easier.

Prior to patch 2.1.2, he was especially deadly to melee characters due to his Frost Pools and Frost Ring being able to overlap, and therefore stack. He also had one more ability:
 * Frost Trail: as Rime moved, he was leaving behind a trail of ice that chilled players and dealt Cold damage over time.