Agnidox

Agnidox is a Rift Guardian, a greatly empowered Demonic Hellflyer. It can only be encountered as a random boss in a Nephalem Rift.

In combat, it gains following abilities:

Since nearly 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 aside from basic melee attack.
 * Fast and Mortar affixes (Mortar has no minimum range, deals increased damage and shoots more lobs)
 * Flame Breath: A short-ranged attack dealing average Fire damage in front of Agnidox, similar to Colossal Firewing's breath. Also knocks enemy back.
 * Charged Fireball: Spits a single, but fast fireball dealing high Fire damage.
 * Fire Volley: Spits three slower fireballs, each dealing average Fire damage.
 * Mark of Fire: Places a medium-size fiery rune on the ground that activates in 2 seconds and lasts 30 seconds. While active, deals high Fire damage over time to anything in it. Can have many at the same time.
 * Flame Nova: Only used when at 50% Life or lower, every 30 seconds. Releases a 360 degrees volley of fire blasts, dealing slight, but hardly avoidable Fire damage.
 * Claw: Melee attack for average Physical damage, only used if nothing else is available.