What's up with that key under the ice in catacombs of Talion?

[Lord Tony]

I've beat the level without collecting that key and I've checked many walkthroughs and guides and none of them mention the key under the ice with the giant fire pit above it

[Dfactor]

The following level is actually about getting it. You return to that area and it's a key item without which you won't be able to finish the last Tibet level anyway.