Primal:Aquis

Among the eternal autumn sunset, deep beneath an endless, poisonous ocean lies the sub-aquatic realm of Aquis. The deadly waters are home to vast sea monsters, but the occupants of this realm, the Undine have worked miracles in order to survive by building their own safe-havens where they can live their lives free from the leviathans and polluted waters of the deep. The occupants of this realm are the Undine, who are able to communicate telepathically and only prosper because of the complex water purification machines they rely on. This humanoid race is perfectly adapted to life underwater with efficient gills and fins that power them through the shadowy depths. Jen's second demon form is based on the Undine race.

Although we assume that the realm of Aquis is that of which is shown when Jen and Scree visit, Aino comments that there are many secret waters far out from the lagoon. It is here the population of the lagoon fled when chaos began to rule.

Scree mentions though he finds the realm to be beautiful, he doesn't know much about the realm and isn't as an expert as he is on Solum.

Lagoon

 * The Temple: It is here we meet the Queen of the realm - Aino. She is about to be sacrificed to the gods of the sea - The Leviathans, however is saved by Jen. It is her that bestows the power of the Undine form upon Jen in blue energy passed through Scree to Jen.
 * The Dam Lagoon: One of the last areas, along with the Temple Lagoon, that still has purified water. The Bay also contains a few beaches, and although picturesque for Jen, are unlikely to have been used by the Undine.

Bay & Tunnels
The majority of the exploration of Aquis occurs here in these two areas that appear to overlap in many places.
 * Sub Stations: Scattered across all lagoons, generally the latter two. It is these sub stations that purify the water, that has helped the Undine race to survive, and must be booted back up in order to restore order.
 * Skeleton Sub-Station: It is here that the sub-station engineer, Aduro, is trapped.
 * Nest Sub-Station: A sub-station that requires to be activated in order to free Aduro. It's also notable for containing a nest of large green eggs which hints possibly to this station being used to purify water for the Undine young.
 * Apostles Mountains: A very large area of dry land that is inhabited by giant crabs. We're never informed of who these apostles are, though it is likely they are Undine. Even so why they have their own mountain and how they were able to traverse it on land is never explained.
 * Undine Statue Cave: A large cave with three towering Undine statues with one resembling The Birth of Venus.
 * Purification Tower: It is here Jen battles [Adaro|King Adaro] and is possible that it was here that he was hiding out, making sure that purification for the entire realm was never turned back on.

Creatures Found in Aquis
Although emphasis is on the Undine, there are a great array of other animals in the realm. Some of these are never mentioned in the game, and as of this Wiki contain non-canon, temporary, descriptive names.

Undine: A telepathtic marine race resembling a mermaid, they govern the waters of the lagoon and are the sentient species.

Fish: Found in all purified waters of the lagoon and of many varieties.

Anemones: These tentacle like things are found in pods covering narrow walls and entranceways around Aquis. Their ability to zap your energy comes from the various barbs over their length, which extends out of the pods as they sense Undine swimming nearby.

Unexplained Eggs: Found throughout the tunnel system, it's not specified what's inside the eggs, but considering they're around one of the purification sub-stations could mean they are actually Undine young. Of course if hatched in unpurified waters, could likely result in them becoming naturally tainted.

Glakk: These are the crabs found on Aquis. Found mainly on dry land, though a few larger crabs are found in water. Come in two castes relating to size - small and large.

Giant Skeleton: A giant skeleton lies in one of the tunnels which leads to the conveniently named: Skeleton Sub-station. Due to it being submerged it is hard to tell what it would look like with muscle and flesh, however it's head looks similar to that of a Tylosaurus Proriger. This monster could be a "Leviathan" Aino spoke of, however she also commented that Leviathans were a type of Undine God.

Trivia
Aquis comes from the prefix, (Aqui-), meaning "water," it's of latin origin, entering the English language circa 1350-1400.