BacQue is a legendary Runeword created by combining a Bac Rune of Ritual and a Que Rune of Invocation.
How to Create BacQue
You can create BacQue by adding the legendary Bac Rune of Ritual and the rare Que Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Bac - Travel 5 meters. (50)
Que - Invoke the Druid's for 3 seconds, granting yourself a Barrier. (300)
Earthen Bulwark
Overflow
BacQue can not overflow because the amount of Offering you receive from the Bac Rune exactly fills the required Offering of the Que Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.