He knew he would die, for the bond was forged and his warrant was written in blood. Pulling that trigger was only part of his penance—penance for what he had done and to save the lives of the innocent while sacrificing not one but two monsters, himself included. Through the power invested in him by the nun, Morgan lay in wait for the demon general to come out of his shambling castle. He waited for him to lower his guard, and he waited for the others to be there so he could ensure that they saw him disintegrate before their eyes.
But as his body fell off the treetop, lifeless and forgiven of past sins, he never would've known that the army and the hero would also be plunged through the tear between dimensions and torn up to bits. From the forest to the edge of the city of Eclanor, everything has been disintegrated into motel glass. Still bubbling with the sheer intensity from a mere speck of the nun's power.
