Grailknights

From left to right: Sovereign Storm, Sir Optimus Prime, Count Cranium, Baron Bigstick, Earl Quake.
Originally formed as Galactic Grailknights. The band jokingly claim to be from a place called Grailham City, and to live in Castle Grailskull. This is a play on Castle Grayskull from the 80s toy range/cartoon series He-Man and the Masters of the Universe.
As part of their comedic "superhero" image, Grailknights' live show features stagehands wearing the costumes of their "nemesis" Dr Skull, and his henchmen Morph the Swarf and Urks the dragon.
Sovereign Storm previously filled in for Lord Lightbringer as a live member before joining permanently in 2011.
Sir Optimus Prime and Mac Death were joint lead vocalists until Death's departure, with Prime taking over all lead vocal duties at that point and reducing his role as guitarist.