So I'm running a homebrew campaign 5th edition, and one of my players is a...bit of an optimizer. Long story short, he found a way to deal several THOUSAND damage by way og spell storing a demi plane, lininging the demi plane with disintegrates, and sending people into the space thus triggering all the glyphs.
Demiplane creates a new plane each casting.
There are a lot of high level situations where a failed save is effectively death for an enemy, regardless of how many hps, defenses or what not they have. They start around 4th level. If I polymorph you into something that is helpless, I can find ways to dispose of you, pretty much no matter what you are (Demiplane is an example - drop something without planeshifting abilities in a demiplane when you have it polymorphed into a worm and then let it starve, etc...)
Don't sweat it.