Devourer caused several Phantom Blasts, leaving mark on Gar. Gar throws some dirty saronite at Devourer, immediately followed by his Thundering Stomp. Devourer produces loose Unleashed Souls. The rush of purple souls is no factor, since they do not pose enough damage to make the dense giant notice. Gar's lack of high level skills leads to downfall. Gar clobbers Devourer with a Thundering Stomp can create a new arm.
Remember: do not turn your back and produce a new weapon during a fight. It is considered bad form and is dumb. While Gar creates the valuable weapon, Devourer whittles him down with more Phantom Blasts, diminishing the big mental midget when he completes the weapon. Gar vents his anger on Devourer, beating him with everything but the frozen kitchen sink. Certainly, Gar's brain is too numb to know that Devourer has locked Mirrored Soul on him, so all of the damage Gar is dishing out he is also taking. Gar pretty much kills himself; Devourer wins.