I started and finished event within 5 minutes of it being released, one of the first!
Alright, so you have to slide about a bit, then leave the ice area, and "Operate" the necklace to summon an ice imp.
You walk in a direction a few steps, and talk to the imp. He will tell you if you are hotter or colder. Remember, you are looking for ice, so you want COLDER!
When you find Jack (hint: north west), talk to him, and you will be taken to fight him. Just slide across the ice into him, then a long cutscene will show Santa being freed.
You will then be teleported back into the real world, with a santa suit + freeze emote, and a snow imp following you for a while.