The Elder Scrolls IV: Oblivion

Game information:

Oblivion is a fantasy-based role-playing adventure game and an example of open-ended or sandbox gameplay. The main quest may be delayed or completely ignored as the player explores the expansive game worlds, following side quests, interacting with NPCs, and developing a character according to their taste. The player is free to go anywhere inside the land of Cyrodiil at any time while playing the game, and even after completing the main quest storyline the game never ends, allowing the player to build their character in whatever way they want, with no restrictions on skills or equipment. The game is open to almost unrestricted modification, and there are hundreds of modifications available on the internet, varying from small weapon changes to complete game overhauls. The game contains many enemies for the player to fight, including monsters and animals. Many enemies, quests, and treasures are "leveled", or become increasingly difficult, as the player gains levels. The player, however, has the option of adjusting the difficulty level.