This is what I think went down in the vault.

So, I believe there was not only one ice lord in there, but more. You see, I believe this because if you look closely at the room's star, you'll notice smudges in the Star of Melody. Those smudges were possibly created by Ice Lords trying to heal the dead Queen Snowfalls. She was then put on a table in the center and 2 Ice Lords went to work. They then resurrected her with Dancebear's stolen powers. Snowfalls woke up with rage and wrote "DD" on the wall possibly meaning "Dooms Day". She then was trapped in those chambers for quite some time along with her fellow King, Raegon. She tried to take off the frozen door spell, but she failed miserably, so she saw the perfect opportunity to get out when we stupidly put the burning crate in front of the door, not knowing what lurked inside the frozen shut vault door. Now as we enter the room I notice that the star of Melody has not one, but two symbols in it. The star of melody, but also another star in it? Hmm possibly DD could have something to do with Damen, or Dancebear?. Here is a picture of it.



That concludes my theory, although it may be whacked up.