CemTun is a magic Runeword created by combining a Cem Rune of Ritual and a Tun Rune of Invocation.
How to Create CemTun
You can create CemTun by adding the magic Cem Rune of Ritual and the magic Tun Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Cem - Cast Evade. (75)
Tun - Invoke the Rogue's Stun Grenades, Stunning and dealing damage to enemies. (100)
Overflow
When CemTun overflows, you receive the Tun Rune's overflow effect (Increased Grenades Spawned) 0.5 times.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.