BacXan is a legendary Runeword created by combining a Bac Rune of Ritual and a Xan Rune of Invocation.
How to Create BacXan
You can create BacXan by adding the legendary Bac Rune of Ritual and the legendary Xan Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
BacXan 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.
Legions
Helltide