Aragorn

Before he shows up in person, Aragorn gets a mention at the end of The Hobbit: The Battle of the Five Armies. After the battle, Thranduil sends Legolas north to find the Dúnedain. He tells him about a young Ranger they call Strider and says Legolas will have to find out his real name for himself.

At the Prancing Pony in Bree, Strider watches the four hobbits from a dark corner. When Frodo slips on the ring by accident, he pulls him into a room and introduces himself as a friend of Gandalf. That night, the Black Riders break into the inn and slash at empty beds.

He leads the hobbits through the wilds to Weathertop. There the Nazgûl attack and Aragorn drives them off with fire and sword, but Frodo has already been stabbed with the Morgul blade. Arwen, the elf he loves, rides in and takes Frodo to Rivendell.

At the Council of Elrond, Legolas reveals who Strider really is: Aragorn, son of Arathorn, heir of Isildur and of the throne of Gondor. Boromir doesn't like it. Aragorn himself is afraid of carrying the blood of the man who didn't destroy the ring when he could. Still, he joins the Fellowship, and Arwen gives him the Evenstar.

After Gandalf falls in Moria, Aragorn takes the lead. At Amon Hen, he lets Frodo go on alone. Boromir dies defending Merry and Pippin, and Aragorn promises him he'll save Minas Tirith. Instead of following Frodo, he decides to hunt the Uruk-hai who took the two hobbits.

With Legolas and Gimli, Aragorn runs for days after the orcs, crosses paths with Éomer and ends up reunited with Gandalf, now the White. In Edoras he helps free Théoden from Saruman's control and travels with the people of Rohan to Helm's Deep. Éowyn falls for him.

In a warg attack, Aragorn goes over a cliff into the river and is given up for dead. He comes back on the horse Brego, warns Théoden that an army of ten thousand Uruk-hai is coming and fights all night at the Deep, alongside Haldir's elves. At dawn he rides out with the king into the enemy, just as Gandalf appears in the east.

When the beacons of Gondor are lit, Aragorn rides with Rohan. At the Rohirrim camp, Elrond arrives with Andúril, Isildur's sword forged anew, and tells him Arwen is dying because her fate is now bound to the ring. Aragorn accepts being king.

With Legolas and Gimli, he takes the Paths of the Dead and demands the ghost army fulfill the oath they broke with Isildur. The dead follow him, arrive on the Corsair ships and, on the Pelennor Fields, sweep away the orcs. Aragorn keeps his word and releases them.

To buy Frodo time, Aragorn leads what's left of the armies to the Black Gate and charges "for Frodo." Sauron falls when the ring is destroyed.

Gandalf crowns Aragorn in Minas Tirith, and Arwen arrives to stay by his side. When the four hobbits bow, the new king tells them they bow to no one and kneels before them, followed by the whole city.

In The Lord of the Rings: The Hunt for Gollum, opening December 17, 2027, Aragorn comes back younger, while he's still living as Strider. Viggo Mortensen isn't returning: the role goes to Jamie Dornan. Andy Serkis directs and returns as Gollum, with Ian McKellen as Gandalf and Elijah Wood as Frodo.

In the books, Strider is 87 when he meets the hobbits in Bree: his people live far longer than ordinary men. He's also much surer of his path than the movies' Aragorn, and most of his backstory lives in the appendices.