Codex of Cinders - Consecrated Ash

You conjure sanctified ash into your hand. For 1 minute your weapon attacks deal an additional 2d6 Radiant damage to Undead.

Against Vampires it has the following additional effects:

• A critical hit prevents mist form for 1 round
• The Vampire can't regenerate until the start of your next turn
• The ash swirls around you, forming a faint circle of glowing embers that flicker with each strike. Any Undead that begins its turn within 5 feet of you must succeed on a Constitution saving throw (DC = 8 + your proficiency + your spellcasting modifier) or take 1d6 radiant damage per turn, as embers cling to their form.