Mage: The Ascension is a role-playing game from the Storyteller series by White Wolf. The game is generally contemporary, but can be played in all ages as the setting is quite flexible. The basic assumption of the game is that reality is malleable: What people believe exist is what actually exist. All player characters in a Mage game are mages, humans with what is called an "awakened will" or "avatar". Using this will, they can locally bend the consensus of reality and produce magical effects.
The system is basically the same as in all Storyteller games. Only ten-sided dice are used: more of them if the character is more able at what is doing, with the score to be rolled on each higher if the action is more difficult.
Like other storytelling games Mage gives the players much freedom in comparison with conventional role-playing games, a power that can be used for deepening the story or simply to "win" more quickly.
Mage's unique point is the powerful magic system (even more free-form than Ars Magica). This poses challenges to players and GM, since a large part of the game is about defining what the character think the world actually is.