Esper

Doctor Cid taps a rhythm out on the wall by her, and those two glass panels slide back into the wall. She reaches up and takes the masks, one in each hand, and turns. "These are the shells of monsters."
"...like turtles? No, that would be silly. If this is the shell, what is the substance?" Linnet asks.
"Sleeping." She pauses. "Which is as inaccurate as one can possibly be while still being true to the spirit of the term. These masks are fragments of the power of the stars, pulled out of the sky for Alterna to trap inside the Great Crystal." She looks at the mask that fades into orange, and shakes her head. "The powers of these stars -- these creatures that spread their vast energy across the night sky -- were used to lock the people of Ducorde on Alterna's chosen path. What we know as Jobs were just shadows of their powers, every single Job pulled from one of these creatures. From the fragments of their most treasured hidden records, we know that the Empress first referred to them as the Guardian Forces. They were known to the rest as Espers." "You mean...one of these was the first White Mage? Or possibly the first everything mage, all in one being? What were they guarding?" Linnet stops herself. "No, sorry, you've answered that. Who or what were they guarding Ducorde and Alterna from?" "On that, the records are empty." She holds the midnight mask up to the light, and then offers it to Linnet. "But yes, the powers of the Crystals stemmed from these Espers. Each with the power of multiple people, some equal to thousands, or hundreds of thousands. Far too powerful for this world. When the Great Crystal shattered, the constellations were once again in the sky, as they should have always been, and as they should remain." "But now something is calling those stars back down here, and bringing untold destruction with them."
There is a source of great power in and above the world of Ducorde. Little is known of the nature of this power, but the power is sentient and fragmented. Called Espers by most and Guardian Forces by the Empress, they served as the core of the Great Crystal's power during the time of Alterna. 
According to the research of Doctor Celadon Isara Dural, sponsor and owner of the Seventh Dawn, the Espers have recently begun falling back to Ducorde from the heavens, and when they arrive, they bring about untold destruction. Espers are completely without ethics or morals, per Doctor Cid, and are exceedingly dangerous to the mortal peoples of Ducorde. 
Espers manifest on Ducorde as masks that bear a resemblance to their 'true' form, or in their true form itself. Cinnabar, the first Esper the party located, first appeared as a mask surrounded by a shadowy cloud of darkness, but was reduced to just the mask when faced with Isa's might. Other Espers have battled the party in their true form, then been reduced to the mask after the battle's conclusion.

GROUPS OF INTEREST

• The Starfall - This ancient Alternan airship carries a projection of the first Empress of Alterna, Relis Laurent, who said that the ship carries The Truth, and Laurent's best chance to "undo the tragedies we visited on the Thirteenth."
• The Rising Stars - headed by Doctor Cid and operating on the Seventh Dawn, this group is dedicated to returning the Espers to the skies above Ducorde by any means necessary, claiming that they will never allow the Espers to control the course of civilization as they did during the time of the Alternan Empire. The Seventh Dawn has multiple masks in its possession.
• Cid Tantalus - A mysterious human man who pointed the party toward Alterna, tasking them with acquiring the Starfall and delivering it to a man in Mechon. Tantalus claimed to be in search of The Truth, and pressed the key to the Starfall into Orrey's hand after waxing poetic about the nature of heroism. According to Tantalus, somewhere in the Starfall resides The Truth.
• The Coda - Saron's secret police, the former eyes of the Empress. Currently run by Aramog Sydney, the Coda is in pursuit of Cid Tantalus, claiming that he stole an Alternan airship.
• The Lumin - Apocynthion Lunakrei and Perilune Roche. According to Apoc, the Lumin are responsible for putting the Guardian Forces into the Great Crystal and therefore spreading them across the night sky. Apoc called Perilune a murderer. Each time the party met Perilune in the open, she was attacked by one of the Espers -- Cinnabar first, Midgardsormr later.

KNOWN ESPERS

(listed in order of encounter)

• Cinnabar - A prancing green rabbit with a ruby embedded in its forehead, Cinnabar encountered the party in Caerwyn when they met Perilune outside of the bar Velvet Sundown. Isa was critical in dispatching it, along with Bast through largely unknown means. Cinnabar's mask, bleached bone with cracked ruby shards in its forehead, has been in Yves's possession ever since. Cinnabar slowly began manifesting itself to aid the party, and notably accompanied them throughout Alterna, showing fear upon seeing the Starfall. Once the ship flew clear of Alternan airspace, Cinnabar vanished, and has only been seen once since.
• Quetzacoatl - A flock of lightning starlings that forms itself into a singular entity. Quetzacoatl swore plural-they would never be caged again and swarmed the party, forcing them to take shelter from its wild rage. Mask as yet unseen. Remains in Alterna.
• (Tree Mask) - A gray and springy forest in Alterna. Yves made contact with the trees, and after showing the forest the Cinnabar mask, was granted a new mask. This one is made of an old and colorless gnarled wood, with two eye sockets, a smooth surface where the nose and mouth would be, and what look like dozens of small branches and twigs extending up instead of hair, almost all of them having broken off.
• (Alternan Storm) - A storm of fire, water, wind, earth, lightning, and ice, kept at bay during the Seventh Dawn's time in Alterna, but returned with a vengeance when the Starfall tried to gain access. The term "Primal Judgment" came to Orrey's mind when observing it.
• Asura(?) - The self-proclaimed Queen of the Eidolons, trapped within the Starfall after Alterna duplicated her powers. She serves as the Starfall's power source, and she contains no small amount of wrath. Discovered by Linnet when Linnet touched the crystal. Yves and Apoc were present when she returned.
• (Beaked Mask) - A beaked mask, extending into ridges of red fur or feathers along the edges, a broken earring dangling down on the left side. In the possession of the Rising Stars aboard the Seventh Dawn.
• (Iron Mask) - An iron mask, almost a helmet beheaded, a weight to it that makes you think that there could almost be a head inside. In the possession of the Rising Stars aboard the Seventh Dawn.
• (Ceramic Mask) - Purple ceramic connected by rough pink stitching, a bulbous, almost sac-like object. In the possession of the Rising Stars aboard the Seventh Dawn.
• Eos - A small mask, a perfect replica of a tiny genderless human face, pupiless eyes, lips slightly parted, bone white at the top, fading into orange at the bottom. Trapped a village in endless sunlight before being stopped. In the possession of the Rising Stars aboard the Seventh Dawn.
• Selene - A small mask, a perfect replica of a tiny genderless human face, pupiless eyes, lips slightly parted, bone white at the top, fading into midnight blue at the bottom. Trapped a village in endless darkness before being stopped. In the possession of the Rising Stars aboard the Seventh Dawn.
• (Chasm Mask) - A mask that is just a wide, open mouth, significantly taller than it is wide, the open mouth painted like a gaping maw to nothingness. In the possession of the Rising Stars aboard the Seventh Dawn.
• (Dragon Mask) - A mask with the top of a dragon skull, the bottom smooth, featureless bone. Given to the Azure Dragoon in the Triad in exchange for a bounty of a box of scarabs. 
• Diabolos - A massive flying serpent, with tendrilled wings along the length of its two-hundred-foot body. Battled the Starfall until entering into a Pact with Yves. Its mask is blackened bone with a rictus grin. In Yves's possession.
• Cerberus - The purpose of Diabolos's mayhem. "Enslaved by mortals for their amusement," according to the serpent. Whereabouts unknown.
• Midgardsormr - Attacked Perilune in Uhja. Father of Dragons, according to Orrey's Libra, and called Perilune the Starscourge. Defeated by the party. Mask is in Isa's possession.
• Marilith - The cause of a forest fire in Perilune's past, before she met the party. She let Marilith burn out before taking the mask. In Perilune's possession.
• Kujata - Killed two people before chasing Perilune away from civilization, whereupon she trapped it in a cave and overcame it. In Perilune's possession.

TRIVIA

• According to Doctor Cid, there are 144 Espers. "Twelve constellations of twelve stars."
• Cinnabar is unique that no Esper has been seen going from mask to manifesting.
• 'Esper' and 'Guardian Force' are terms that have been used interchangeably thus far; if there is a difference between the two, the party has yet to learn the difference with the information they have found.
• According to Doctor Cid -- a recurring trend on the information the party has available thus far -- the Espers were the source of every Job within the Alternan Empire's Job Crystals.