Thanatos isn't a scientist, so he wouldn't be able to really help. Besides, he has more important things to focus on.

"Far from it. I cannot reach the surface, so it's up to Charon and Hermes to bring the shades to the Underworld." Thanatos sighs, and Mort climbs to his shoulder to nuzzle Thanatos's cheek. "They can be fast, but the sheer number who should be dead is... unthinkable."

The work had really, really piled up since his absence.