Third Degree Burns

Causes

Fire Damage Injuries 
Radiant Damage Injuries

Symptoms

You have disadvantage on ability checks and Constitution saving throws. If you fail a saving throw against an effect that causes fire damage, you also gain the stunned condition until the end of your next turn.

Treatment

Magic healing of 6th level or higher cures this damage. Alternatively, if someone tends to the burns and makes a DC 15 Wisdom check (Medicine), they will heal on their own in 21 days.