UrMot is a rare Runeword created by combining a Ur Rune of Ritual and a Mot Rune of Invocation.
How to Create UrMot
You can create UrMot by adding the magic Ur Rune of Ritual and the rare Mot Rune of Invocation to a two-socketed Helm, Chest Armor, Pants, or Two-Handed Weapon.
Ur - Your Minion or Companion kills an enemy or dies. (10)
Mot - Gain 1 |4 shadow:shadows;, from the Rogue's , reducing damage taken per shadow. (150)
Dark Shroud
Overflow
UrMot can not overflow because the amount of Offering you receive from the Ur Rune exactly fills the required Offering of the Mot Rune.
Overflow occurs when your Ritual generates more Offering than required for the Invocation. The overflow effect is proportional to the amount Offering overflows.