As I'm working on my gravity compendium, I went and revisited Elden Ring for some inspiration. I'll be honest I didn't remember the entire moveset of this guy, but after some research, here's a fully usable Alabaster Lord.
The CR is fairly low and he doesn't have legendary actions, since it becomes a regular enemy later on, and he is not fast enough that legendary actions would feel appropriate.
I'm currently working on a Soulsborne Inspired D&D Setting called Steinhardt's Guide to the Eldritch Hunt. If you're interested, Join the Hunt Here.
You'll join a mailing list and receive the Oath of the Eldritch Hunt Paladin. No worries I promise not to spam, I hate that stuff. I'll only be sending free content your way, once per week in a neat package.