Naglfar

Naglfar (ナグルファル) is a spell used to control ships, based on a ship of the same name from Norse Mythology which was constructed from the nails of the dead and would be used to ferry the hordes which would battle the gods at Ragnarok.

Principles
As Naglfar was constructed from the fingernails and toenails of the dead, the spell requires nails from dead people.