This is the official info from the Keep it True homepage:

As promised we can now reveal the first headliner for KEEP IT TRUE 13 in April 2010. It will be swedisch Doom legends CANDLEMASS with a very special show.

CANDLEMASS will play a very special 2 hour show at KEEP IT TRUE 13 and are going to perform their classic “Epicus Doomicus Metallicus” album in its entirety with original vocalist Johan Langquist on vocals as part of their set to celebrate their 25th anniversary of the band. The regular set will feature Rob Lowe on vocals.