Protagonist
Eragon is the protagonist of the Inheritance Cycle. He is also known as Eragon Shadeslayer, Argetlam, Shur'tugal, Firesword and Kingkiller. Eragon is the son of Selena and Brom, although Eragon's relationship to Brom is not revealed until later, until which time he is thought to be the son of Morzan. Eragon is the cousin of Roran Garrowsson. He was raised as a farm-boy for fifteen years under the care of his uncle Garrow. Then, a few months before his sixteenth birthday, the last female dragon in Alagaësia, Saphira, hatched for him. His uncle was killed by the Ra'zac, and he leaves Carvahall to seek revenge with Brom, the storyteller with a secret life. He later finds out that Brom was a dragon rider, but Brom is mortally wounded by the Ra'zac and his death greatly affects Eragon. Eragon is rescued by Murtagh and they journey to Gil'ead to find the Varden, where they rescue Arya, and then flee to the Varden at Farthen Dûr. Eragon also finds out that he is the last hope for Alagaësia to rid the great land of the evil of Galbatorix.
Antagonist
Galbatorix is the main antagonist in the Inheritance Cycle. He is the traitor that brought about the destruction of the Riders before the series began. When his first dragon, Jarnunvösk, is killed by Urgals, and he is not allowed another one, the enraged Galbatorix turns against the Riders. He recruits Morzan, first of the thirteen Forsworn, to his cause, and with his help steals a dragon hatchling and uses dark magic to bring the dragon, Shruikan, under his control. He recruits more members of the Forsworn as he sets out to destroy the Riders, and derives his growing magical strength from the captured souls of dead dragons, the Eldunarí. Galbatorix and the Forsworn destroy the old order of Riders, including their leader Vrael, and Galbatorix anoints himself King of Alagaesia, enslaving hundreds of Eldunari and using their vast magical reserves to stay in power. The destruction of the Riders spreads war, madness, and chaos throughout Alagaësia. A hundred years later, almost all human lands are under Galbatorix's control, and he seeks to destroy or subjugate the other races (elf, dwarf and Urgal). It has been said that three elves, one a dragon rider and two spell-casters, have discovered his true name, but he put a spell around his name that kills anyone who uses it, so he cannot be magically controlled.