A demo of the song "The Deceived" was included on the re-release of Trivium's debut album Ember to Inferno nearly a year before Ascendancy was released. Likewise, a demo version of "Like Light to the Flies" was included on the MTVcompilation albumHeadbangers Ball Volume 2. Also, a demo of the song "Blinding Tears Will Break the Skies" was included on the Ember to Inferno re-release and later re-recorded and included as a bonus track on the re-release of Ascendancy.
Since its release, Ascendancy has sold over 500,000 copies worldwide. In the U.S., the album peaked at No. 151 on the Billboard 200 and at No. 4 on the Top Heatseekers charts, selling over 140,000 units. In the UK, it peaked at No. 78, and shipped over 100,000 copies, attaining Gold status, without entering the UK top 75.
Upon its release, the album received critical acclaim. Brandon Ratliff from 411mania, gave the album a perfect review, saying this about the band, "Watch out for this band twenty years from now. They will be as influential to so many as bands like Sabbath, Slayer, and Metallica were before them. As I said before, this album is in every way perfect, and that’s why I am proud to announce the first album to ever get a perfect score from me. Now go and buy this album. If you like metal at all you will.". In another very positive review, Johnny Loftus of Allmusic had this to say about the album, "Ascendancy aligns real-deal thrash with powerful modern influences. But at all times it's a platform for Trivium's own crazed talent."