Homebrew
Soul Rot
1-level Necromancy
Casting Time: 1 reaction (which you take when a creature within 60 feet is reduced to 0 hit points)
Range/Area: 60 feet
Components: V, S
Duration: Instantaneous
You siphon lingering death magic. Choose one creature within range. That creature takes 2d8 shadow damage and gains vulnerability to shadow damage until the end of your next turn.
Available for: Warlock