Yliaster are engine-like constructs designed by the dragons, either to be equipped on as prosthesis' or implanted into a human body. They were originally developed as artificial limbs for hosts of physical mutations, but their present applications have expanded to include strengthening of the mind and body, forcefully empowering one's own physical, spiritual and mental capabilities on a scale relative to the amount their body hosts.
At present, a significant number of Genesis Division members own Yliaster (amongst numerous others), which give a strong impression of heightened battle strength. These machines were meant to make up for lost bodily functions without being rejected or overburdening the body.
Yliaster Synthesizers can be implanted into the body to synchronize with Calculation and Information Accumulation Turbines, thereby obtaining all sorts of information. They're activated by touching Calculation Engines and focusing one's consciousness on them. Beginners' Yliaster Synthesizers are tiny things implanted into the head (the occipital lobe to be precise) and any scars from the surgery are covered up by hair. In exchange for the risk of losing one's lives in failed surgeries, one can become able to heighten their Yliaster Synthesizer's productivity. The "high class" Yliaster Synthesizers prohibited by the Upper Tier require surgical replacement of portions of the brain. Those surgeries have an exceptionally high failure rate, but when they succeed, those humans become able to control most Calculation Engines and gain supernatural information handling abilities.
The substitution surgery used to implant Yliaster is colloquially dubbed "Enginization." There do exist some Lower Tier Citizens who Enginize themselves out of convenience, but they're different from those with "over forty percent of the body Enginized." They're said to be at extremely high mental and physical risk, but there are very few of them. If one becomes a completely Enginized "Engine Human," it's rumored that one could annihilate foes usually twice their regular power level. However, the burden placed on the brain and the mind is amazing, and no successful instances of a complete substitution surgery have ever been recorded.
The more economical Yliaster (dubbed E-Yiliaster) supply various forms of mechanical power, perform high level calculations, and even manage information. They appear all over every Tier of Tenryūji. They're External Combustion Devices, and the greater the size, the greater the output. Mansions and factories, as well as some merchant homes, are allowed to set up large- and medium-sized E-Yiliaster. At the level of an ordinary subject or citizen, a small-sized device exists in each house. In addition, it's become a habit for thieves to steal Yliaster Energy. The most popular targets are the City Administration's power conduits. They're used to power the large machines under their management in each Tier.