Fool's Gamble

There's a species that carries a terrible curse-they are assigned a human at birth and given the responsibility of holding each of their human's reincarnated souls. They lock them in their being so that their human's may not go insane from the memories or the multiple souls they've had. They are echoes with no purpose other than to contain. Until someone slipped through their watchful eyes, killing them and releasing the many lives back into their humans. Earth is not safe, humans have been swallowed by insanity, unable to keep apart their many lives with multiple souls fighting for dominance in one body. Only a handful of guardians are left alive. What will become of earth and all the souls in it?