Illuminas are mysterious cores that Tavoo and members of W.I.S.E. use in the future. They seem to be grafted onto or inside their bodies. As Shiner stated, they have the ability of amplifying their host's Psi powers numerous times, slowing the aging processes of their bodies, replenishing their Psi energies by gathering more from the atmosphere of the future world, and eliminating the natural needs of their bodies (such as nourishment). On the other hand, they are also an important weak point as they seem to be fragile and removing them is fatal for the user. As such, destroying the core turns the host into ash in a matter of moments.
Dholaki is the first to have grafted two of the Illuminas on his body, after his first defeat by Ageha Yoshina. This process, as stated by Shiner, is extremely dangerous as few people survive grafting a second core on their bodies and, even if the procedure succeds, they have a less than 5% chance of surviving another year. The process of grafting two illuminas on a persons eventually lead to the creation of the Scourge elite unit which showed better results in the few who survived.
Oboro also has multiple spheres, resembling Illuminas, but much smaller, grafted onto his hands. It is unknown, as of yet, to their identity and his condition.
Kasukabe, a Tavoo and former researcher for the W.I.S.E. stated that if sunlight were to fall upon those who have undergone Illumina Forge, they would suffocate as if oxygen has been taken from them.
The illumina was gifted to W.I.S.E. by Mithra with their real purpose to gather energy from their hosts that will ultimately by transferred to Quat Nevas.