Manntis originally formed in 2000 as a four-piece group. The band gathered mainstream attention in 2004 when they were one of the contestants on MTV's Battle for Ozzfest. Their lead guitarist, Adair Cobley, was picked as the representative for the band on the show. Ultimately, Manntis finished in third place (behind Curse Your Name and eventual winner's A Dozen Furies).
On April 1, 2005, it was annoucned that the band signed a worldwide deal with Century Media Records. Their debut album Sleep in Your Grave was released on June 28, 2005. The tracks "Axe of Redemption" and "Weathered Souls" were released as singles, with music videos accompanying each.