Ichor

Ichor is the golden blood of all immortal beings. Those with ichor, including gods, Titans, and some monsters are near-perfect beings who, in battle, can be wounded, but never permanently killed, or in the case of gods and Titans, can never be killed at all. Demigods also share their godly parent's ichor in their veins infused with their human blood, however, it cannot be seen, and it does not make them immortal.

Ichor in demigod's bloodstreams may let them live longer than a regular mortal, but this is yet to be seen as most demigods die early from getting killed by monsters.