“Your character is a hero, and his death will have meaning.”
In most situations, if you fall to 0 hp, are captured, or even fail all your death saves, your character will not be removed from the game. He or she is a hero. And a hero will fall down, and get back up again.
There are a couple of exceptions: A player can ask for a heroic death to be pre-planned, ask for a retirement, or simply ask to create a new character and ask the DM work it into the plot. The final way is when the GM says something is Dire Peril. If those words are uttered, it means that the situation, through design or chance, will contain the potential for permanent death.
When you gain a level, you lose all hero points, and gain a new total equal to 5 + your level.
You can spend a hero point whenever you roll a d20 to make an attack roll, damage roll, an ability check, or a saving throw. You don’t have to decide until after you make the roll and learn if it succeeded or failed.
If you spend an action point, roll a d6 and add it to your d20 result, possibly changing a failure into a success. You can spend only 1 action point per roll.
In addition, whenever you fail a death saving throw, you can spend an action point to make it a success.
Each player starts with 1 plot point. Once every player has used their plot point, all players receive another plot point.
A player who spends a plot point gets to add some element to the setting or a situation that the group must accept as true.
For example, the player may spend a plot point to say they found a secret door, a NPC appears, etc.
As a twist, with the GM approval, the payer to the right may need to add a complication.
For example, the player might say that the secret door is trapped, or that the NPC arrives with an arrest warrant. These complications will not always occur.
A shield gives the normal bonus to AC, however, there is another advantage shields have.
Wits profeciency, a shield can be used as ablative armor, rather than just an AC bonus.
A shield can be sacrificed/splintered/broken to avoid damage on a hit completely. A critical hit could be erased completely, at the loss of the shield. This even works against spells with an attack roll.
A shield master can even use this against spells where he failed a normal saving throw.
Psychic shields used by Thoon can use this effect, but due to psychic feedback they will be unable to summon the shield again for a long rest.
Magic shields, if discovered, can also be damaged in this way, though they are much stronger. They can do this a number of times before they are destoryed, but each time, it threatens the magic contained in the shield.
When struck with a critical hit, the Pc will retain a scar, even after healing. Higher level healing spells can erase or fix these scars, but in the meantime, hey, you have a story.
The player of the PC has the option of narrating where they are hit, and the scars that result. This is mostly just narrative coolness.