Harsher Sun is a small Vampirism addon that makes sunlight more dangerous for vampires. Whenever a vampire is taking sun damage, they are also set on fire, adding fire damage on top of the normal sun damage, with a sizzling sound and smoke particles. The flames go out instantly once sun exposure ends, and fire from other sources (like lava) is unaffected. Works on both players and vampire NPCs, with config options to toggle mob burning, the sizzle sound, and smoke particles.
Requires Vampirism 1.10+ on NeoForge 21.1.236+ for Minecraft 1.21.1.