I don't know if this is due to the fact that the Mayhem website is shit, but they haven't mentioned either on the official site or the Facebook that Betraying The Martyrs is part of the festival. I hope I'm wrong, but I think they the replacement band.
5/2 The Body/Full Of Hell/Kowloon Walled City/Children of God
10/10-11 California Deathfest
FM Doom: Thursday 2-5PM PST! KSJS.ORG