[The most beautiful and beloved of the gods, Balder, son of Odin, had been slain by his blind brother wielding a misletoe shaft aimed by Loki. Balder's wife had joined him on the funeral pyre. After their funeral, they were in the world called Niflheim.]
An attempt was made to resurrect Balder, but due to more of Loki's mischief, it failed.
The goddess of death, Hel, promised that Balder could return to earth if every living creature shed tears of grief for Balder. It looked as though it would work, for everyone loved Balder, but Loki arranged for a single exception. Loki disguised himself as the giantess Thok. As Thok, Loki was too indifferent to cry. And so, Balder could not return to the land of the living. Balder and his wife remained in Niflheim.
Another son of Odin, Vali, revenged the death of Balder, but not by getting back at Loki. Instead, Vali slew his brother, the blind god Hod. Loki, who had fled the initial scene of Balder's death in Gladhseim, and then re-appeared in disguise as the giantess Thok, tried to get to safety by turning into a salmon. The salmon-Loki hid in a waterfall. But the Aesir, who knew where he was, tried to catch him in a net. Loki was too clever for that and jumped right over the net. Thor, however, was fast enough to catch the leaping fish in his bare hands. Then Loki was bound in a cave with venom dripping onto his body, which caused him to writhe in pain -- until the world's end in Ragnarok. (See Prometheus for a similar punishment.)