Frozen Gate is a skill located in the Winter's Embrace (which can be found in the Warden skill tree). Frozen Gate is a base skill, and can be morphed into Frozen Device or Frozen Retreat.
Frozen Gate deals the following types of damage: Frost Damage. Which means that it gets buffed by the following blue champion point trees: Elemental Expert, Elf Born, Spell Erosion. Also the following red champion point trees protect against this skill: Elemental Defender.