UrXan is a legendary Runeword created by combining a Ur Rune of Ritual and a Xan Rune of Invocation.
How to Create UrXan
You can create UrXan by adding the magic Ur Rune of Ritual and the legendary Xan Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Ur - Your Minion or Companion kills an enemy or dies. (10)
Xan - Your next Skill cast will be a guaranteed Critical Strike and Overpower. (700)
Overflow
UrXan can not overflow because the Xan Rune does not have an overflow effect.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.