YulThul is a legendary Runeword created by combining a Yul Rune of Ritual and a Thul Rune of Invocation.
How to Create YulThul
You can create YulThul by adding the legendary Yul Rune of Ritual and the rare Thul Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Yul - Cast a Skill with a Cooldown. (50)
Thul - Invoke the Sorcerer's , inflicting Freeze and Vulnerable onto enemies. (300)
Mystical Frost Nova
Overflow
YulThul can not overflow because the amount of Offering you receive from the Yul 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.