Complex sentence: Before judgement can be passed on Loki, the heroes learn that the dark god Surtur has reforged the Twilight Sword and plans to use the chaos caused by Loki in order to launch his own invasion of Asgard.
Split into simpler sentences: Before judgement can be passed on Loki, the heroes learn that the dark god Surtur has reforged the Twilight Sword. Surtur plans to use the chaos caused by Loki in order to launch his own invasion of Asgard.