What is sickening radiance?

Sickening radiance is a 4th-level necromancy spell in the game Dungeons & Dragons. When cast, it creates a sphere of greenish light that fills a 30-foot radius sphere for a duration of 10 minutes. The light causes sickness to creatures that are exposed to it, causing them to become nauseous and take radiant damage. Any creature that starts its turn within the sphere or enters the sphere for the first time on a turn must make a Constitution saving throw or suffer damage. Additionally, the light will cause disadvantage on attack rolls and ability checks for any creature entirely within the sphere. However, the caster will also suffer damage when they cast the spell and each subsequent turn they remain within the sphere. As a 4th-level spell, Sickening Radiance is a formidable weapon when used correctly, but it can be dangerous for the caster if they do not plan carefully.