CemChac is a rare Runeword created by combining a Cem Rune of Ritual and a Chac Rune of Invocation.
How to Create CemChac
You can create CemChac by adding the magic Cem Rune of Ritual and the rare Chac Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Cem - Cast Evade. (75)
Chac - Invoke the Druid's Lightning Bolt, striking a nearby enemy. (20)
Overflow
When CemChac overflows, you receive the Chac Rune's overflow effect (Increased Bolts Spawned) 2.75 times.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.