Who they are is kinda confusing. Chi is the red one, and Phi is the green one. They are the Starseed Gardeners, but they also go by the Garden Crystal Senshi, or Garden Senshi. This garden that they are refurring to is a garden of spiky starseeds in Galaxia's palace at Zero Star Sagitarrious. Sense they are always apologizing for the failures of the other minions, you can kindof consider them as the leader of the Animamates/minions. They protect the crystals that Galaxia has collected.
They are probably the strongest of all of Galaxia's followers, and this I will agree with! They are very close to Galaxia in a sense because it is obvious that they are the most powerful, trusted with the Garden Crystal, and wear sun symbols that represent Galaxia.
They are all throughout the Stars Volumes of Sailor Moon. They are the ones that kill Lethe and Mnemosyne, take their seeds, and the Starlights two.
Kakyuu and Moon gained up to Kill Phi, but Phi turned around and killed Kakyuu for the loss of her sister. Moon, sad for Kakyuu, did kill Chi shortly after. The Asteroid Senshi helped her of course.
~Back to the Chi and Phi Shrine~