Sickening Radiance

Dim greenish light spreads in a 30-ft. radius sphere centered on a point within range. When a creature enters for the first time on a turn or starts there, it must make a CON save or take 4d10 radiant damage, subtract 1d4 from its next d20 test before the end of its next turn, and emit dim green light that prevents invisibility until the effect ends.