If your character has at least 1 remaining spell slot and knows that they are about to drop to 0 HP you have the option to take a reaction to burn all your remaining spell slots, inspiration points and death saves to bestow a Death Curse.

This is a powerful, dangerous ability that should not be taken lightly.

To do so means you immediately fail 3 death saving throws and your body is utterly destroyed as it is burned up to ‘fuel’ one last spell.

This spell can replicate any spell up to your highest remaining spell slot + 2 per point of inspiration – up to a Level 10 Wish.
For example:
if you have 3 first level spells you can cast a 3rd level spell.
If you have a 8, 2x 3 and 4x 1 level spells you can cast any spell up to 9th level.

Naturally none of these spells can be used to ‘heal or revive yourself’ as it wouldn’t be a ‘death curse’ if you didn’t die in the casting :P

Your characters True Name is written into the Dead Book.
From here your character can only be revived via a 9th level True Resurrection, though one was known to be brought back via Wish after making a deal with Death.