CirVex is a legendary Runeword created by combining a Cir Rune of Ritual and a Vex Rune of Invocation.
How to Create CirVex
You can create CirVex by adding the magic Cir Rune of Ritual and the legendary Vex Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Cir - Cast the same non-Channeled Skill 3 times in a row. (50)
Vex - Gain +3 to all Skills for 7 seconds. (1000)
Overflow
CirVex can not overflow because the amount of Offering you receive from the Cir Rune exactly fills the required Offering of the Vex Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.