City in the Dust
In keeping with the epic and heroic nature of the campaign as planned, your characters will gain 5 + half level hero points each level as per the rules in the DMG on page 263.
Each point can be spent to enhance an attack roll, ability check or saving throw after the roll is made but before success is decided. Spending the hero point allows the player to add a 1d6 roll to the initial d20 roll.
Any unspent hero points are lost when the character levels and a new total is gained.
In addition, when a player fails a death save, spending a hero point can turn the failure into a success.