Heaven Sailors

"They're beautiful..."
-Primarch Marais, of Miranda
The Heaven Sailors are a species of jellyfish-like creatures native to the deep regions of the Mastaar Galaxy. They are attracted to praxis, and have such a fine sense for it that when Earth underwent the Cataclysm, nearly all sailors in the entire Mastaar Galaxy sensed it, and changed course. 
Nowadays, the sailors travel to the Sol System in rotations. They always appear on New Year's Eve, and travel away a week later. Some scientists have theorized that this rhythm comes from the people celebrating New Year's Eve, and the collective mana that generates from those feelings of renewal and celebration is something they find delicious. 
The sudden shift in the migratory patterns of sailor colonies is what attracted Tzan'Kai and other explorers to Earth. 
Though the sailors are extremely massive, some growing to the size of the moon Charon, they are harmless and passive. Whether they have intelligence is a matter of debate. As they have no central nervous systems, primarily consisting of a bioluminescent, jelly-like film, some scientists believe them to be creatures of mere instinct. At the same time however, the sailors have been observed performing actions that may be considered communication with one another, and seem to recognize individual people, hinting at a deeper layer to the mystery.