User blog comment:Chichiryuushintei/High School DxD BorN Episode 5 Review/@comment-3290441-20150503143819/@comment-3290441-20150503173900

No the term Deus ex Machina, or Machine of God, refers to the story element where a unexpected or unforeseen thing that appears at the end of a story to save the protagonists without being foreshadowed or mentioned earlier. It refers to the fact that in many ancient plays a god of some sort would come in and save a protagonist from a hopeless situation.

True in the light novels that did happen with the unforeseen appearance of the ahem "Chichigami" if my Japanese is correct, but Vali appeared near the beginning of the volume proposing a alliance to take down Loki and did snatch up Fenrir abandoning the group.

The difference is a matter of timing, granted it wasn't the end of the episode, but it was the end of the battle against Loki.