TamXal is a legendary Runeword created by combining a Tam Rune of Ritual and a Xal Rune of Invocation.
How to Create TamXal
You can create TamXal by adding the legendary Tam Rune of Ritual and the rare Xal Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
TamXal can not overflow because the amount of Offering you receive from the Tam Rune exactly fills the required Offering of the Xal Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.
Legions
Helltide