Base Class: Warlock
One who has made a pact, a covenant of sorts, with a goddess of death, in order to enact vengeance for something they've lost.
Based on the game Valkyrie Profile: Covenant of the Plume.
Level 3: Plume's Covenant
Once per long rest you may increase the ability scores of one of your allies to 20 in all stats. however, after 5 minutes their ability scores return to normal, and they are reduced to zero HP with 1 death save.
You must complete a long rest before you use this feature again.
Level 3: Angel Slayer
Once you have used Plumes Covenant 5 times, you gain access to a weapon known as the Angel Slayer, and can use it for the next 5 minutes, or until you fall unconscious, after which you must use Plumes Covenant 5 more times to gain access to the Angel Slayer again.
Angel slayer (Longsword)
The Angel Slayer functions like a regular, magical longsword. However it has the following additions: The Angel Slayer has advantage against Celestial beings such as Angels. And the Angel Slayer doubles its damage die once per person that actually dies after Plumes Covenant is used by them
Level 6: Angel Slayer Improvement
When you gain this ability, the Angel Slayer weapon doubles its current damage die count, regardless of what its currently at.
Level 10: Angel Slayer Improvement II
The effect of this is identical to the first Angel Slayer Improvement.
Level 14: Angel Slayer Improvement III
You get the gist.