Speak with Jaron Stoneshaper in Starfall Village.
The story behind Kel'Theril is one of a cursed race, bound to the place where they attempted an unfortunate ritual...
The highborne that you will find there once stole a sacred artifact, believing that they could siphon its power for themselves, becoming even more powerful. In their efforts, the relic shattered in a huge explosion, driving the pieces below the ice of the lake...
Speak with Jaron Stoneshaper if you'd like to learn more; he has recently visited the area and can tell you more.