Utgard-Loki

"... There we were, moored up by the Ice Needles, when old Utgard-Loki blew its stack, cracking the outer facade of ice."

- Arngrim Dammen on one of his escapades

Utgard-Loki is a location mentioned in the Comic, "The Ice Castle", and is located in the Northlands.

Geography
Based on the commentary of Arngrim Dammen, Utgard-Loki is an active volcano next to the Ice Needles. Based on his commentary, Utgard-Loki contains the Labyrinth of Lost Souls beneath or next to it. The volcanic and geothermal heat is presumably the source of sulfur and heat for the adjacent Jotun Hot Springs.

Dragons: Riders of Berk Comics
In "The Ice Castle", Arngrim Dammen mentions Utgard-Loki when boasting about his escapades to the Hairy Hooligans.