Board Thread:Episode Discussions/@comment-25787298-20160519120227/@comment-25549954-20160519201658

Chakra is basically a mixture of Spiritual energy (mind) and Physical energy (energy produced by cells of the body) If that energy is sapped out they die, my best guess is that Hagoromo taught them to mould these two energies to create chakra for use. Kaguya was the first person to mould these two energies on Naruto's planet.