Quasilumins are the remnants of the civilians of the Celestial Capital of Al'Taieu, which separated from Vana'diel in a great cataclysm. In appearance, Quasilumins are no more than scintillating orbs of light, and no Quasilumin is known to have a unique name. They often speak without emotion, even robotically.
Al'Taieu, Grand Palace of Hu'Xzoi, and The Garden of Ru'Hmet
If an adventurer speaks to all of the Quasilumins in one of the three main areas of Lumoria, and then the final Quasilumin a second time, the Quasilumin will grant the adventurer a map of that area. There are 20 Quasilumins in Al'Taieu, and 10 each in Hu'Xzoi and Ru'Hmet.
Grand Palace of Hu'Xzoi
In Hu'Xzoi, there are also four Cermet Alcoves that each spawn a mobile Quasilumin. Players must escort the Quasilumins to their destinations, protecting them from harm, so that they may open doors along the way that are otherwise impassable. This is necessary for the Chains of Promathia mission A Fate Decided, for reaching Quasilumin NPCs to acquire the map of the Grand Palace of Hu'Xzoi, and also for fighting certain Notorious Monsters in the grand palace.
Abyssea - Empyreal Paradox
In the alternate realm of Abyssea, Lumoria rests on the surface of the Abyssean moon, but the Empyreal Paradox has separated from the rest of the Celestial Capital, and is the only portion of Abyssea's Lumoria accessible to players. In it, there are two Quasilumins. One is an Atma Infusionist, offering to imbue players with the effects of their collected Atma key items, and the other Quasilumin is a Cruor Prospector, offering temporary items and status enhancements in exchange for cruor.
Quasilumin is Latin for "as if light".