Helena actually surviving and her ability to fake her injuries/death is subtly foreshadowed in her boss fight with Mario when she's shown getting hit by her traps and only taking a little bit of damage. These traps just to remind you include lighting the entire room in burning hot fire and spawning spikes up from the ground to impale the unfortunate victim, and these are extremely fatal. In spite of her powers, Helena for all intents and purposes does not seem to be physically much more stronger than Mario. So had she actually got hit by her own traps, she wouldn't take little bits of damage, she would've died immediately.
Fridge Horror
The No Save Ending in the Arc expansion finally brings peace to Mario as Len choosing to free him from the cycle of rebirth and allows him to live his life, while presumably finally letting Marchionne's soul rest in peace. However, it should be noted that it's possible to get this ending in the Sane Route where Riba has truly lost it and had been revealed to have survived his fight with Mario, or in the Insane Route without Riba doing a Heel–Face Turn, which means that unless Len decided to do something about himnote which is very unlikely considering this is Len we're talking about, the "good ending" in Arc still consists of a sadistic, homocidal demon just freely roaming the world with nothing stopping him from manipulating or killing more people.
Assuming Envy is able to accurately mirror the emotions/feelings of those it turns into, this leaves some pretty horrifying implications of Luigi's mental health.
It's stated in the game that the undead tend to haunt/kill their victims in a manner similar to how they themselves died, and we see a few examples of this such as when the girl in the bathroom drowns Mario or how Mercy at one point attempts to pull Mario into the furnace to burn alive. This makes the implications of how Marie died extremely horrifying.. especially when you remember that one of the two people responsible for the deaths of the family is a homocidal, man-eating demon.
Also on the topic of this, the way Beatrice died might be extremely horrifying. We know from the remastered game that she isn't a member of the Adurarice family, in fact she was already long dead before Alice and Riba went on their murderous rampage. With that in mind, it's possible that she might be from Evangeline, and who's the one spirit there that's shown using a pair of scissors to kill Mario in a death scene? Yeah... Beatrice may have been subjected to horrific Cold-Blooded Tortureas a little girl.
So, it's stated that if you die in Helena's mental world, you'll die in the real world, aka if you die in your sleep you'll never wake up. But, we don't really know how something like that would affect an immortal demon like Riba. In the Insane Route, if you didn't kill Riba earlier, Helena will capture him and trap both him and Mario in a dream, where she will offer to let Mario go if he allows her to kill Riba. The best case scenario here is this is just the same as killing Riba normally, and he'll just revive once again. The worst case scenario is you're either killing Riba for good or putting him in a state where he's technically alive but unconscious and unable to wake up ever again.note Of course, the Fridge Horror is a little downplayed considering this is Riba we're talking about.
With Mario declaring Mercy as Beyond Redemption, it's entirely possible that her soul will never be put to rest, even with Alice's attempts to make it up to her.
