Hello, I'm from Thailand. I have a question about Aasimar's Celestial Revelation skill when used in conjunction with the feat: Vital Sacrifice, which states "When you attack or cast a spell that hits the target..." You will deal additional Necrotic damage 2d6". I wonder if the additional damage dealt will equal your Proficiency Bonus as well?

For example, Eldritch Blast(Agonizing Blast)+hex(Celestial Revelation)+Vital Sacrifice(Celestial Revelation)=1d10(3)+1d6(cha mod)+2d6(cha mod or not)

Celestial Revelation.

When you reach character level 3, you can transform as a Bonus Action using one of the options below (choose the option each time you transform). The transformation lasts for 1 minute or until you end it (no action required). Once you transform, you can't do so again until you finish a Long Rest.

Once on each of your turns before the transformation ends, you can deal extra damage to one target when you deal damage to it with an attack or a spell. The extra damage equals your Proficiency Bonus, and the extra damage's type is either Necrotic for Necrotic Shroud or Radiant for Heavenly Wings and Inner Radiance.

feat: Vital Sacrifice

You've learned secrets of hemocraft that grant you esoteric power at the price of your own life force. As a bonus action, you can choose to take 1d6 necrotic damage to gain a blood boon. Your blood boon lasts for 1 hour or until expended.

 You can expend this blood boon to gain one of the following benefits:

 When you make an attack roll, you roll 1d6 and add it to the total.

When you hit with an attack or spell, you deal an additional 2d6 necrotic damage.

I am very sorry to inform you, but this is the wrong forum for this sort of question; this would fit better in Rules and Discussions

Thank you for telling me. I've never used it before and didn't know where to ask.

Quote from preutake >>

Thank you for telling me. I've never used it before and didn't know where to ask.

 you are fine, it's an honest mistake