This thread has given me an idea for a new magic item. Probably Common, certainly no higher than Uncommon, but I think it could be a nifty little thing to have.
Amulet of Scourging Fire
This amulet must be worn next to the skin. At the start of your turn, if you are affected by a hostile condition that can be ended by taking damage, the amulet activates, dealing 1d4 fire damage to you. You can also activate the amulet (no action required) at any time on your turn, but the amulet cannot activate more than once per turn.
If the amulet would deal enough damage to reduce you to 0 hit points, the damage is reduced so that it leaves you at 1 hit point instead. If this would reduce the damage to zero, the amulet does not activate.