It contains alternate re-ordered versions of all the songs from their EPLifesblood, as well as the three tracks from their 7" debut EP Slick Leg. Both originally released in 2001 and a bonus song, "Call of the Mastodon", which has only appeared on the 9 Song Demo, which originally contained vocals by their previous vocalist Eric Saner.
This was their final release on Relapse; they subsequently signed to Warner Music.
On the documentary of the making of Crack the Skye, the band stated that Call of the Mastodon is their FIRST studio album, (Brent lists it first before Remission, Leviathan, Blood Mountain). He doesn't mention anything about it being their third album. He just says Crack The Skye is their fifth album *IF* you count Call of The Mastodon as their first.