"Immortal (Su)

At 9th tier, if you are killed, you return to life 24 hours later, regardless of the condition of your body or the means by which you were killed. When you return to life, you aren't treated as if you had rested, and don't regain the use of abilities that recharge with rest until you next rest. This ability doesn't apply if you're killed by a coup de grace or critical hit performed by either a mythic creature (or creature of even greater power) or a non-mythic creature wielding a weapon capable of bypassing epic damage reduction. At 10th tier, you can be killed only by a coup de grace or critical hit made with an artifact."

At: https://sites.google.com/site/pathfinderogc/mythic/mythic-heroes