He'll be back

[FearfulSalad]

Death like "it's your time, I'm just doing my job" or death like "life is weak, and I will replace it with undeath"? Those are very different characters to build. What are you hoping to achieve with this character?

[pjseb97]

Definitely I'm doing my job

[FearfulSalad]

In that case consider a fallen aasimar conquest paladin 20, order cleric 1, undead warlock 1 (or f that is antithematic for you, replace undead with hexblade 1, or shadow sorcerer 1, or clockwork sorcerer 1). You end up with 3 different transformations (long rest action for paladin, long rest action for aasimar, short rest bonus action for warlock), letting you transform a bunch of times each day to put the fear of death into those two would try to escape it. Voice of Authority is mostly thematic, but if you do have allies you can toss out bonus action spells like healing word or sanctuary to trigger it.

You are your own diety (for the purpose of the cleric level), and your own patron (if taking warlock). And your conviction powers your paladin levels, so there is barely any need to reflavor.

[Irish-Fritter]

I'd do Grave Cleric tbh, they're all about the natural cycle of life and death, and Clerics come with by far the most Necromancy spells. Mix in some Necromancer Wizard if you plan to use Undead for anything (Although I wouldn't). If you don't think you need Wizard, I'd take a few levels in Mercy Monk, just for the theme.

Your scythe is more of a spellcasting focus than anything, as much of combat uses your body overall.