KaaTal is a rare Runeword created by combining a Kaa Rune of Ritual and a Tal Rune of Invocation.
How to Create KaaTal
You can create KaaTal by adding the rare Kaa Rune of Ritual and the magic Tal Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Kaa - Lose 1% of your Maximum Life. (2)
Tal - Evoke the Spiritborn's Pestilent Swarm, dealing damage to enemies. (100)
Overflow
KaaTal can not overflow because the amount of Offering you receive from the Kaa Rune exactly fills the required Offering of the Tal Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.