Purging Dagger
This chiseled wooden dagger is a relic crafted from the bough of a holy tree and is always miraculously sharp. You gain a +1 bonus to attack and damage rolls made with this magic weapon. The dagger deals an extra 1d4 radiant damage to any target it hits. The extra damage increases to 2d4 when you use the dagger to attack an undead creature, causing blue tongues of holy flame to flash along the weapon’s edge.
When you roll a 20 on an attack roll made with this weapon against an undead creature, you can choose to plunge the blade into the creature’s body and leave it there. When you do, the dagger emits bright light in a 15-foot radius and dim light for another 15 feet. The light is sunlight. While the blade is lodged in a target in this way, that target takes 3d4 radiant damage at the start of each of its turns, and the dagger continues to emit sunlight. A creature can use an action to make a DC 16 Strength check, freeing the dagger from the target on a success. Once freed, the blade vanishes and reappears on the ground at your feet or in your hand if you have one free.
In the depths of the vampire's lair, sunlight was a welcome ally. The creature's screams echoed around the chamber as its hands slipped, one after the other, from the dagger's wooden hilt. The sickening sizzle and hiss of its undead flesh against the weapon's edge was reward enough for their troubles.