(I feel like Deus Ex Machina is hated so badly that I can almost hear thunder in the background just by typing it) Ok, here's the thing: I have an MC who is saved from death by a magic item (one which an important character spends several years off camera getting, and which only serves one use and purpose), but whose use causes a rift between her and the one taking care of her (she thought her friend was truly trying to kill her, the item only caused her to think she was dying so the villain would leave. She reacts by killing her friend when she wakes up, thinking it was a failed attempt on her life). Does this sound too unpleasant as a Deus Ex Machina? The problem is that standing before the villain (and this part is necessary) would be akin to frodo standing before Sauron (with only Samwise at his side at best), no way to survive and no way out. The problem is that the item itself is never mentioned or brought up (although magic items with single use are known and rare) EXCEPT in this circumstance (another magic item is witnessed earlier in the story, but it's pretty much useless and is only there to let the readers know they exist).