ZanTal is a magic Runeword created by combining a Zan Rune of Ritual and a Tal Rune of Invocation.
How to Create ZanTal
You can create ZanTal by adding the magic Zan Rune of Ritual and the magic Tal Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Zan - Cast an Ultimate Skill. (150)
Tal - Invoke the Spiritborn's Pestilent Swarm, dealing damage to enemies. (100)
Overflow
When ZanTal overflows, you receive the Tal Rune's overflow effect (Increased Swarms 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.