From the publisher's web site:
Released over time by the Bureau of Epic Affairs, these classes represent the various advanced beings of Athas. If you want to be a mover of worlds, this is where you look.
A beta release of Legends of Athas is now available. This is a playtest release of 6 epic prestige classes, including the Athasian dragon and the avangion; more than 30 new epic feats; over 30 epic spells and power; over 30 artifacts, both conversions and brand new ones; as well as a collection of epic monsters. The final version of LoA will include stats for Athasian epic NPCs, including all sorcerer-kings; details about Athasian epic organizations; and more epic spells and monsters.
Please submit playtesting feedback to templarate@lists.athas.org.