IgniThul is a legendary Runeword created by combining a Igni Rune of Ritual and a Thul Rune of Invocation.
How to Create IgniThul
You can create IgniThul by adding the legendary Igni Rune of Ritual and the rare Thul Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Igni - Stores offering every 0.3 seconds. Cast a non-Basic Skill to gain the stored offering. (Up to 500 Offering). (25)
Thul - Invoke the Sorcerer's Skill, inflicting Freeze and Vulnerable onto enemies. (300)
Mystical Frost Nova
Overflow
IgniThul can not overflow because the amount of Offering you receive from the Igni Rune exactly fills the required Offering of the Thul Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.