Originally Posted by Webfoot Hero
I sort of think that the Casket of Ancient Winters will be be in play. Last we saw of it, Loki had it in his possession and I don't exactly remember Odin or Thor taking it from him. Maybe on Loki's travels, he stashed it or gave it to Malekith for some grander plan.
Loki had placed the Casket onto the device that activated the Bi-Frost Bridge, which is the reason why we saw the place being frozen up with that interesting looking icicle tree inside of it. The casket most likely fell into the darkest part of the cosmos when Thor destroyed the bridge.