During the attack, L and Light ended up separated in the confusion. L was caught alone by Diablo, who attacked him with a warped version of his Meister in an attempt to steal his soul. When Light caught up with L, and found him fighting a losing battle, he stepped in to intervene in the only way he could think to - by attempting to use his meister ability of Soul Manipulate on Diablo to keep his creation at bay long enough for L to escape. His amplified ability allowed L's soul to remain intact, and, when they joined their forces to fight proper, L's elation at being snatched away from death by his once-murderer lent their resonation unusual levels of clarity and strength for the rest of the struggle.