KaaLum is a rare Runeword created by combining a Kaa Rune of Ritual and a Lum Rune of Invocation.
How to Create KaaLum
You can create KaaLum by adding the rare Kaa Rune of Ritual and the magic Lum Rune of Invocation to a two-socketed 
Helm, 
Chest Armor, 
Pants, or 
Two-Handed Weapon.
Overflow
When KaaLum overflows, you receive the Lum Rune's overflow effect (Increased Resource Restored) 0.2 times.
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