Updated: Nov 1, 2021
Another way to call this spell would be: how to start a low magic campaign!
The DC of the spell is set at 20 to keep baby sorcerers in mind. With their 10 CON at birth, they would always die if the DC was higher. You can change it to be the spellcasters DC like normal spells do if you wish to.
As you can guess it involves quite some work in order to get such powerful magic to function.
Now why would someone cast such magic is the real question. In a world where dragons have access to spellcasting that could perhaps kill a majority of them, although with their CON save perhaps not.
It could also be used to ferment your power, since weaker casters would be wiped out, and only the strong ones would remain, with very little chance of someone rising up to destroy you.
I also wrote rules on how to cast 10th level spells, which you can find by Joining us on Patreon!
Art: Burn from Within by James Ryman