Consequences at Zero Hit Points

For many adventuring parties being knocked unconscious is a penalty only if you actually miss your turn. There are so many healing abilities that spending more than a round at 0 hp is often a long-forgotten memory after 4th or 5th level when healing word and revivify become de rigueur choices for your bard, druid, cleric, and celestial soul sorcerer. 

This can keep combat quick and smooth, but also has the disappointing effect, noted at gaming tables worldwide, of making combat a kind of nothing event in most cases. If there's no consequence beyond using a 2nd-level spell slot for being reduced to 0 hp, why try to avoid it? 

The answer in this case is to reintroduce consequences for reaching 0 hp without crippling a character. There are several ways to do this, three of which are presented here.

Secret Death Saves. If you play online, the players whisper them to you. If you play at the table, they hand you a note. Or you trust them enough to manage it by themselves. Keep also secret if the character made it or not. A successful DC 10 Medicine Check reveals, if the character is still dying, stable or dead. This leads to RP and to intense fights.

Lethargy. Falling to 0 Hit Points gives one level of exhaustion. That prevents the feeling of being an indestructible machine that keeps fighting after being revived several times - dying either slows you down to recover, or you have to operate at limited capacity, and if you fuck up enough times you've beefed it anyway (e.g., if you're at Exhaustion 6 and dead, you're not coming back).

Broken Armor. Falling to 0 Hit Points gives the characters armor class a permanent and stackable malus of -1. If your armor class falls to 10 because of that, it breaks apart entirely. To repair the armor, it costs 1/10 of the armors original price per point of AC that must be restored.