Still have testing to do, but pls give feedback!
5pc Winterborn (Chest, Waist, Legs, Feet, Hands) Light
(2 items) Adds 967 Max Magicka
(3 items) Adds 129 Magicka Recovery
(4 items) Adds 129 Spell Damage
(5 items) When you deal damage with a Cold Damage ability, you have an 8% chance to summon an ice pillar that deals 7967 Cold Damage to all enemies in a 3 meter radius. The ice pillar persists for 2 seconds and reduces the Movment Speed of all enemies within the radius by 60%.

2pc Iceheart (Head, Shoulders) Heavy, Medium
(1 items) Adds 688 Spell Critical
(2 items) When you deal Critical Damage, you have a 20% chance to gain a damage shield that absorbs 8600 damage for 6 seconds. While the damage shield holds, you deal 770 Cold Damage to all enemies within 5 meters of you every 1 second. This effect can occur once every 6 seconds.

4pc Mothers Sorrow (Ring, Ring, Neck, Ice Staff)
(2 items) Adds 967 Max Magicka
(3 items) Adds 688 Spell Critical
(4 items) Adds 688 Spell Critical