BacZec is a legendary Runeword created by combining a Bac Rune of Ritual and a Zec Rune of Invocation.
How to Create BacZec
You can create BacZec by adding the legendary Bac Rune of Ritual and the rare Zec Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Bac - Travel 5 meters. (50)
Zec - Reduce your active Ultimate Cooldown by 2 seconds. (200)
Overflow
BacZec can not overflow because the amount of Offering you receive from the Bac Rune exactly fills the required Offering of the Zec Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.