Planescape - Fool's Road
Damage normally leaves no lingering effects. This option introduces the potential for long-term injuries. It’s up to you to decide when to check for a lingering injury. A creature might sustain a lingering injury under the following circumstances:
- When it takes a critical hit
- When it drops to 0 hit points but isn’t killed outright
- When it fails a death saving throw by 5 or more
To determine the nature of the injury, roll on the Lingering Injuries table. This table assumes a typical humanoid physiology, but you can adapt the results for creatures with different body types.
(Pg. 272 DMG)
DM Note: I will always call for a roll when you drop to 0 hit points, however not all critical hits will call for a roll on the Lingering Injuries Table