(The following information is taken from the manga and the anime itself, mostly paraphrases of statements made in canon)
The Scab Coral
The Scab Coral is an ancient parasitical life-form which embedded itself into the planet's core many years ago. It's indigenous to the Earth and lives within, its own life-force connected to the planet's. It's breath is called trapar, which exists in the air as a reflective light that is invisible to humans. Light Finding Operations (or LFOs for short) can travel on the trapar using ref-boards that reflect off the light. This method of travel is very similar to surfing, only in the air and using invisible light waves instead of water.
The Scab Coral is very much sentient and wishes to coexist with human life on the surface of Earth. It's regarded with fear and astonishment amongst the few humans who are familiar with it. Any strong connection or direct contact with the Scab results in what is called "desperation disease". The symptoms that go along with desperation disease are quite simple: no response to any outside stimuli. Another common symptom is the longing stare directed at a compac drive, which is the fandom's way of powering devices. (Compac drives are used in vehicles and LFOs, which were created to read trapar and communicate with the planet) What is actually going on with desperation disease is that the person's conscious is existing inside the core of the Scab Coral and cannot be reached in any fashion. The blank look on the victim's face is what gives the condition its name.
Coralians
"Coralians", in structure, are comparable to coral in the ocean, only far more sentient and evolved. They were said to have grown because of the other animals and earth they devoured in their early stages, which was done in a desperate attempt to evolve and rise to the top of the food chain. Basically, their fear of the world around them drove them to their existence in the present.
In essence, "Coralians" are children of the Scab Coral. There are many classes and sub-classes, but the two most common are the
"Antibody" Coralians and the
"Kute" Coralians. Antibody Coralians are males, which only arise from the Scab when they're ready to reproduce with the Kutes, which are the females. Antibody's take the form of eyeballs (purple with a red line, like Anemone's and Eureka's) while Kute's take the form of a large gray cloud. Trapar is in high levels around them and is often too much for any vessal to handle. In their rising, Antibody Coralians are very bloodthirsty and destructive*. The Scab's survival takes precedence over everything else, because if it dies, the entire planet will die. Kute are able to be penetrated by the most skilled of pilots, in which case, the vessal will entire the "Zone", which is the gateway to the Scab's conscious and core.
The final class of Coralian is a "Human-Form" Coralian, of which only two exist: Sakuya and Eureka. They are the planet's true attempt to communicate with human life. The human-form coralians were sent as human-looking teenagers, simply 'found' on their own. They know nothing except what is needed to survive, much like a human baby in a teenager's body. They learn through their interactions with humans, thus bringing humans and coralians closer to one another.
Only when they find their true match do they finally smile and show signs of coexistence. Eureka's match is with Renton Thruston while Sakuya's is with Norbu of the Voderak.
*Another strange factor of all coralians is their desire to devour everything. It seems that, as a majority, a 'true coralian' believes that eating something will make them apart of it. This explains their bloodthirsty nature and Anemone's personal desire to eat things that she likes (ex: If she eats sweets, she herself will become 'sweet')
Anemone's Relation with the Scab Coral
Anemone is an artificial human-form coralian, an exact duplicate of Eureka, created by Colonel Dewey Novak. As a child, she had desperation disease and a very strong connection with the Scab Coral. In order to bring her out of her coma of sorts, she was given a drug on a regular basis. After a while, she became independent and only needed the drug on certain occasions, like when her headaches (caused by her forced separation from the Scab) got too much to bear.
Her treatment in the military was very harsh, being treated more like an experiment and a monster than an actual human being. Because of this, she never really learned to bond and still has a child-like mindset when dealing with the world around her. She also lacks real compassion for anything but herself because of this. She was bred as a weapon, never meant to think or feel for anything. Her only attachment seems to be that of Colonel Dewey (for bringing her into existence) and to Dominic Sorel (for waiting on her hand and foot). Her relationship with Dominic is an odd one, for she seems to hate him with all her being, yet cries out for him when she is alone.
Anemone doesn't understand why she was brought out of the Scab and back to consciousness, or what her drugs are for. In fact, it's likely that she's very unaware that she's living outside the Scab at all. However, she's quite aware of the fact that she was once human, now coralian.
Anemone and her medication
Anemone's medication brings out the coralian in her, soothing her headaches and other ailments. However, it makes her extremely bloodthirsty and sadistic, leaving her completely helpless in controlling her actions. It is injected into a receptor on her neck, which links to her jugular and feeds straight into her bloodstream. When injected, it's quite painful for her, thus, she does not enjoy them when they are used. In addition to this, they ravage her mind and body, making her physically weaker in mind and body once they ware off.
She is not permitted to pilot Nirvash typeTheEND without it, thus, has a negative attitude towards sky combat in general.
Nirvash typeZERO and Nirvash typeTheEND
Nirvash typeZERO is a LFO created by the Scab itself as a sentient vessel designed to bring Eureka and her partner through the Zone and back to the planet's core. It's purpose was to complete the journey for the two and solidify the bond between humans and coralians so they might exist together on the same planet. At first, Eureka was able to pilot it without a Compac Drive, due to her connection with the Scab. However, once Renton was discovered, it would not work without the Compac. The theory is that the Nirvash desired to communicate with Renton, but was unable to do so without a compac (because he's not a coralian).
Nirvash typeTheEND is a copy of typeZERO, designed by Dewey for Anemone. It too is a replica, though works in the same fashion as typeZERO and is sentient towards Anemone. However, it was revamped by the military for combat use, and is used for such. It requires no compac and can only be controlled by Anemone and Dominic, just like typeZERO can only be controlled by Eureka and Renton.