For the Hollow One mythic path from Mythic Paths of the Lost Spheres:
Eldritch Interment (Mythic)
You awaken the energies of your blood-magic by infusing it with the essence of creatures possessing you.
Prerequisites: Have experienced or are currently under the effect of a possession attack by a creature, Brandish the Black mythic path ability.
Benefit: While possessed you awaken your blood to the powers of the creature within you. You gain access to any bloodline (sorcerer or bloodrager, your choice) affiliated with the creature. Your effective level for this bloodline is equal to your twice your tier to the limit of your hit dice. If you possess this bloodline from another source you instead may add half your tier to your bloodline level and may ignore the hit die limit. If you are a spontaneous caster you may add bonus spells for the new bloodline to your spells known.