In the Prose Edda, a narrative of Norse mythology, by the Icelandic historian and poet Snorri Sturluson, Loki was depicted as the son of giant Farbauti and giantess or goddess Laufey and a cunning trickster with the ability to change his shape and sex. Represented as the companion of his sworn brother Odin and the great god Thor, he was known to be a Trickster God for his love of playing pranks on both his fellow gods or their opponents, which sometimes caused embarrassment and difficulty for the gods and himself. Apart from being the father of a son named Nari or Narfi with his wife Sigyn, Loki fathered another three, one each with the giantess Angrboda, the Midgard Serpent, who coils around the world, and Hel, the goddess of the Underworld.
In addition to that, according to a strange mythological story of the Fortification of Asgard, Loki changed his shape and sex to become a mare and gave birth to the eight-legged horse Sleipnir, fathered by the giant stallion Svaðilfari. However, the birth of Svaðilfar has a strange background behind it. According to the story, Loki played a major role at the time of rebuilding the Fortification of Asgard. The story says, when the Gods urgently needed to rebuild the walls of Asgard, destroyed after the Aesir-Vanir war, a frost giant in disguise appeared before them with his huge and powerful stallion Svaðilfari and proposed to rebuild the fortifications of Asgard within a specific time, if he is awarded the beautiful goddess Freya.
Despite their initial refusal, the Gods finally agreed to accept the proposal of the unknown mason, at the repeated insistence of Loki and much to the dismay of Freya, who refused to be traded as a sheep. However, soon the Gods became amazed and terrified by the surprisingly rapid progress of the wall and started to blame Loki, who assured them to take it easy. He observed that during the nights the huge stallion is used to bring a great number of stones towards Asgard to make the job easier for the mason. Loki immediately hit upon a plan and to divert the attention of the stallion and appeared before him in the shape of a beautiful mare. Svadilfari, the stallion leapt with excitement, broke the steed to make himself free and ran after the mare, which took flight through the forest, while the great builder cursed after the mare. The process continued night after night and the artificer soon realized that he would not be able to complete the job in time. He exploded in rage, knowing well that a plot had been laid by the gods against him and entered the forest intending to kill the sheep. But the gods were watching at him from the bushes and Thor, the mighty thunder god leapt over the giant and crushed him under his powerful blows. However, the ensuing 'act of love' led Loki to give birth to the eight-legged horse Sleipnir.
On another occasion, by his recklessness, Loki ended up in the hands of a furious giant, Thiazi, who threatened to kill him unless he brings him Idun, the beautiful Goddess with long golden hair, the Goddess of spring and eternal youth. However, after he fulfilled the condition imposed by the giant for the sake of his life, Loki found himself in a tight corner when the gods threatened him with dire consequences unless Idun is rescued.
This time again Loki used his ability to change his form and shifting his shape into that of a falcon, he carried the goddess back to Asgard in his talons. Although the furious Thiazi desperately pursued him in the form of an eagle and almost caught up near Asgard, the gods lighted a fire around the perimeter of their fortress. Ultimately, the flare of the flames caught Thiazi and burned him to death, while Loki reached the halls of the gods safely with Idun. On this particular occasion, Loki surely came to the aid of the gods, but only to rectify a calamity for which he is responsible.
However, Loki was instrumental in the death of Baldur, one of the brothers of Thor, who was loved by all the Gods. When his death was prophesied, Baldur’s mother, Frigg, secured a promise from every living thing in the nine worlds, except the seemingly harmless mistletoe or the hemi parasitic plants, not to harm her son. Upon discovering this omission, Loki carved a dart made of mistletoe and during a celebration when the Gods were testing the invulnerability of Baldur, gave it to the blind god Hodus, the twin brother of Baldur. As all the big weapons, even the axes of Thor failed to hurt Baldur, Loki asked Hodus to throw the dart which instantly killed Baldur. After the unexpected tragedy, the gods sent Hermod, another son of Odin, to Hel, the queen of the Underworld, with a request to release Baldur from her realm, as every living thing was in inconsolable grief over the loss of Baldur. However, Hel inherited her dark nature from her father Loki and inclined to find pleasure in depriving others of their deepest desires.
So she played a cruel trick and informed Hermod sarcastically that she would only consent to release Baldur if he could confirm her that every last thing in the universe wept for Baldur. Hermod gladly accepted the proposal, as Baldur was loved by all, went around all over the Nine worlds and got almost everything in the cosmos to weep for Baldur, except one giantess, who was probably Loki in disguise. That sealed the fate of Baldur as Hel refused to release him to return to the real world and kept him in her cold clutches. Nevertheless, the incident eventually exposed the negative side of Loki that ultimately led to a battle between good and evil known as Ragnarok.
Loki alternately helped both the gods and the giants, depending on which course of action seemed most pleasurable and advantageous to him at the time. However, after the heartbreaking incident of Baldur, he was captured by the other gods for his involvement in the matter, apart from his many other actions that went against the Gods in general. He was tied with a chain made from the guts of his son to a rock with a poison-oozing snake suspended above him. This was too much for Sigyn, the wife of Loki, who placed herself beside her chained husband, holding out a bowl to catch the drops of venom from the suspended snake and thus save his face. However, when the bowl becomes full and she leaves to pour out the venom, Loki becomes exposed to the dripping snake. As a result, he writhes in pain and agony and starts to shake violently that creates an earthquake and in the process, makes the chains gradually loosen around him. The process continued until Loki became successful to break the shackles, signifying the setting the Ragnarok into motion.