Gollum, originally known as Sméagol (or Trahald), is a character in Middle-earth: Shadow of Mordor and the Middle-earth: Shadow of War. The game's protagonists, Talion and Celebrimbor, meet Gollum on their journey within Mordor.
Gollum was initially known as Sméagol when he was a Stoor (also known as the River folk). He lived an unnaturally long life due to possession of the One Ring; he was about 589 years old at the time of his death. In The Hobbit, he was described as a small, slimy creature.
He spent the early years of his life with his extended family under the matriarch, his grandmother. On Sméagol's birthday, he and his relative Déagol went fishing in the Gladden Fields north of Lothlorien. There, Déagol found the ring after being pulled into the water by a fish. Smeagol immediately fell under the Ring's spell and demanded it as a birthday present, strangling Déagol when the latter refused to hand over the ring. Constant exposure to the Ring twisted him, ruining his body and twisting his mind. He developed two separate personalities, one representing what was left of Sméagol (dubbed "stinker" by Samwise Gamgee), and the other representing the malign influence of the Ring. Sméagol used the Ring for stealing from, spying on and antagonizing his friends and relatives. When he wasn't using it, he hid the ring in his throat, resulting in the distinctive choking sound he occasionally still makes. The townsfolk nicknamed him "Gollum" for that reason, and eventually banished him. He then made his way to an island at the center of an underground lake hidden deep within the Misty Mountains. He survived mostly on cave fish, which he caught from his small boat, but when he thought he could get away with it he used the Ring to hunt small goblins who strayed too far from the stronghold of the Great Goblin.
Gollum left his cave in pursuit of Bilbo a few years after losing the Ring, but the trail was cold. He made his way to the edge of Mordor, where he met the monstrous spider Shelob and became her spy, leading Uruks and other creatures into her nest in order to avoid becoming food himself.
During the events of Shadow of Mordor, Talion and Celebrimbor seek him out in order to shed light on the identity of the latter. When they locate him, Gollum swears to serve the Bright Master. While Celebrimbor believes he can be a valuable asset, Talion does not trust the creature.