Hero Points and Mythic Power
At 1st level, all characters begin play with two Hero Points. As characters advance, they gain one additional Hero Point at 4th level, and again every 4 levels thereafter. A character can have no more than three Hero Points at any given time. Hero points can be used in one of two ways. They can be spent, in which case they are regained at the beginning of the next session, or they can be burned, in which case they are used permanently. Uses that burn hero points typically have a more significant impact than uses that spend them temporarily.
Ways to Spend Hero Points
As an immediate action, gain a +4 bonus on a d20 roll before the die is thrown.
As an immediate action, gain a +2 bonus on a d20 roll after the results are revealed.
As a move action, recover HP equal to Constitution score.
As a move action at the beginning of your turn, attempt a new saving throw against any one condition affecting you. You may take this action even if you are otherwise incapable of acting (for example, if you are dazed), and even if you would not normally be allowed a saving throw against the effect that caused it (e.g. Power Word Stun).
Ways to Burn Hero Points
As a free action when you would die from HP damage, you instead fall unconscious and stable at -1 HP. You will suffer lasting injuries depending on the form and amount of damage at the DM's discretion. These can typically be healed with restoration or regeneration magic, though in extreme cases it may require a wish or miracle to undo. This use does not apply to death by Constitution damage or death effects. This use requires two hero points.
As a free action, re-roll a d20 roll after the results are revealed.
As an immediate action, force an enemy to re-roll an attack or saving throw after the results are revealed.
Mythic Power
Should your GM decide to use the Mythic rules, you can find them here. When a character ascends into myth, they lose all hero points they possessed, and no longer gain hero points; this fledgling power is overshadowed by the new power that suffuses them. If for some reason, they lose their mythic powers, they regain two hero points and earn them at the usual rate.
A character may permanently burn their uses-per-day of mythic power in the same way they would burn a hero point, at the same cost in mythic uses (e.g. you may burn one mythic use to force an enemy to re-roll a saving throw). See Ways to Burn Hero Points, above.
If a hero burns all their uses-per-day of mythic power in this way, they permanently lose their mythic powers. Unless they find a different source of power, they are normal mortals once again.