His Destiny With Fëanor
When Melkor's sentence in chains had been served, he was released and then sought to take revenge by turning the Noldor against the Valar and against each other. Fëanor, although he did not trust Melkor, was entangled in his lies and began to speak of rebelling against the Valar. This caused unrest in Tirion, so Finwë summoned all of his lords to council. Fingolfin came first and warned his father of Fëanor's growing influence and threat to his reign. Fëanor, who arrived soon enough to hear this, was infuriated and drew his sword on his brother, saying, "Get thee gone, and take thy due place!" Fingolfin bowed to his father, without paying any heed to the threat from his brother, and departed. Fëanor followed him to the door of the king's house and held the tip of the sword to his brother's chest, and said, "See, half-brother! This is sharper than thy tongue. Try but once to usurp my place and the love of my father, and maybe it will rid the Noldor of one who seeks to be the master of thralls." This proclamation was heard by man who were around, but Fingolfin answered not and passed through the crowd, in search of Finarfin.
The Valar punished Fëanor with a twelve-year banishment from Tirion. Fingolfin offered pardon from the sentence, "I will release my brother", but Fëanor remained silent and left. Finwë left Tirion with his firstborn son and Fingolfin became the lord of Tirion. Fëanor was later invited to a great feast, marked by the ripening of the fruits of the Trees, to honor Eru. There, he met Fingolfin again, who reminded him of his offer, "As I promised, I do now. I release thee, and remember no grievance." He then took Fëanor's hand and swore, "Half-brother in blood, full brother in heart I will be. Thou shalt lead and I will follow. May no grief divide us." To this, Fëanor replied, "I hear thee. So be it."
With the slaying of Finwë and the sacking of the Silmarils, Fingolfined maintain his promise to Fëanor, hesistantly, to follow Morgoth and reclaim both the Silmarils and honor. Finarfin joined Fingolfin, and the three brothers lead the Noldor on a journey out of the Blessed Realm. They saved Fëanor's host at Alqualondë, in the Kinslaying and the plight over the white ships of the Teleri.
Fingolfin, however, was soon betrayed by his brother. When they had gone far north and neared the straight of Helcaraxë, Fëanor betrayed him by taking his own host across the narrower part of the Great Sea and abandoning his brother and those who followed him. Fingolfin refused to return to Valinor in shame, so he led his people on a bitter march through the horrid, icy path. This is among the greatest obstacles faced by the Noldor, as many died, but at last, Fingolfin led his people back to Middle Earth. As they arrived, the Moon rose for the first time, and Fingolfin's trumpets sounded. The synchrony of trumpets and the Moon frightened many of the Orcs of Morgoth, so they retreated into the Angband. Fingolfin marched unopposed through Dor Daedeloth and his legions pounded upon the gates of Angband. Maedhros heard them and called for release from his imprisonment, but none could hear him.
Seeing that the defenses of Angband were too powerful, Fingolfin treated back to Mithrim, where Fëanor's Noldor resided. Fearing strife from the betrayal, and in shame, the Fëanorian Noldor retreated to the southern shores of Lake Mithrim, with Fingolfin's group occupying the other side.