Valti is one of the locations of importance mentioned by Marianne, a Vir space colony, and the colony closest to Earth. According to what Claire once told Marianne, it is actually KIC 8462852, a star with notable fluctuations in brightness. Scientists on earth cannot explain this with absolute certainty, with theories ranging from an exceptional amount of exoplants, to meteors, to an artificial dyson swarm (the last of those turns out to be the case).
Valti is of particular importance because it is the location of a Magico leviathan's attack, which destroyed a habitat and took countless lives doing so. The attack united the humans and the vir in their quest to destroy the magicos, but even though the alliance won, Valti is still full of dormant cores orbiting the stellar remains.