Eventually, a man named Brom easily discovers Eragon's possession of a dragon, and offers to help him. Eragon, after a plethora of arguments and listing benefits he could gain easily, reluctantly accepted Brom's help and together they travelled the vast lands of Alagaësia. On the way, we meet many new characters, the most significant ones being Arya (an elf from the Varden) and Murtagh (a son of one of the thirteen Forsworn). Arya was found severely damaged and ill, while also in a coma. Brom dies along the way by being attacked and he is soon after buried with a sandstone tombstone which was transformed to pure diamond to honour him and his virtuous deeds. The Varden is where Arya is from, and they were on the riders' side, thus leaving Eragon one choice: to travel and find the Varden. Entering was very tedious and dangerous, as the Forsworn were an enemy of the Varden and Murtagh was related to them. However, they all managed to get past and Murtagh proved his loyalty.
However, the Urgals (a brute-like ogre) attacked the homeland of the Varden and consequently a brutal war broke out. A shade (a creature, almost like a human, but extremely difficult to defeat and very rare) also appeared, which was the leader of the Urgal army. Eragon killed him, and he was labelled as "Shadeslayer". However, he was left with a colossal vertical scar up his back after this. When he was unconscious after killing the Shade, another mind contacted him. The story ends there.
(Please acknowledge that I did miss out a many, many details. Feel free to ask questions.)