Cosmoenergy

Cosmoenergy (コスモエネルギー kosumoenerugī) or cosmopower (コスモパワー kosumopawā) is the energy generated by the burning of one's cosmo. Its visible part is called an "aura".

Saint Seiya Anime
Cosmoenergy is the primary life force in the universe, used by every living being (even after dead in the case of humans) and heavily associated to senses. Saints and other warriors, gods, and some select others can use the cosmoenergy to awaken senses above the regular ones necessary for life. When that happens, cosmoenergy can be used to perform superhuman feats.

Eagle Marin is who tells Seiya about how she should use the energy inside of his body, calling cosmoenergy.

The cosmoenergy is extremely strong and powerful, but the user must be careful, because if large amounts of energy are used, it could cause tiredness even death.