Changes
Corrected factual error: the Radiant damage type was introduced in 4e, not 5e.
From the first time the sun rose, every living creature has either loved or feared its warmth and power, burning in the sky. As magic was learned and shaped, among the first spells to be cast were those for fire to burn away our enemies and create warmth for us in the winter, and of light to chase away the darkness. Clerics and some wizards use the light of the sun to deadly effect, blasting undead abominations to pieces and scorching the flesh of the wicked.
Radiance is a new damage type, or rather, a new name for an existing, nameless damage type, given a name later in 5e4e. Spells like ''[[SRD:Searing Light | Searing Light]]'' deal Radiant damage, searing flesh and overloading the soul with power.
Against undead creatures, creatures tied directly to the plane of Shadow (Such as Shadar-Kai), fungi, and oozes, Radiant damage increases by one die size - So from 1d6 to 1d8, for example. Against creatures particularly vulnerable to sunlight - Such as Vampires - Radiant damage instead increases by two die sizes - So from 1d6 to 1d10, for example. These increases in damage do not stack. Some specific effects may have a different increase in damage against these types of creatures; If they do, use those values instead.