Atum 2 is a mod by Team Metallurgy created and designed by Shadowclaimer and programmed by Girafi. It adds a new dimension for the player to explore.
It is possible for the player to start in Atum instead of the Overworld, if they choose, because of this there are various vanilla equivalent components in the mod, allowing a player to access most of the same items as if starting in the Overworld.