Frost Damage is a blue spell component under the Offense tree that deals ice elemental damage along with a slight slow to anything hit.
"Many underestimate the power that frost can wield. The creeping chill can bypass many armors, and frost is devastating against the denizens of the nether. Frost damage also applies a brief slowing effect when it hits" -Arcane Compendium
Frost Damage deals a strong amount of magic damage to the target alongside a subtle slowing debuff.