ZanTun is a magic Runeword created by combining a Zan Rune of Ritual and a Tun Rune of Invocation.
How to Create ZanTun
You can create ZanTun by adding the magic Zan Rune of Ritual and the magic Tun Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Zan - Cast an Ultimate Skill. (150)
Tun - Invoke the Rogue's Stun Grenades, Stunning and dealing damage to enemies. (25)
Overflow
When ZanTun overflows, you receive the Tun Rune's overflow effect (Increased Grenades Spawned) 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.