The Ignis (イグニス, Igunisu) are AI with free will from the Yu-Gi-Oh! VRAINS anime, created by Dr. Kogami through the Hanoi Project. They created and inhabit the Cyberse. According to Varis, the Ignis are out trying to conquer the network. For this reason, the Knights of Hanoi led by Varis are trying to kill all the Ignis with aid in this mission from Dr. Kogami's avatar.
Ignis are humanoid life forms that are smaller than a Duel Disk, though they can change their size and appearance at will. Ai displayed the ability to morph itself into a large, monstrous form with a single eye when it needed to devour data.
Many of the Ignis were captured by the Knights of Hanoi. One of the Ignis tried to rescue the others, but he was caught and eaten by "Cracking Dragon". He survived, but lost most of his data (including memories and body) and was reduced to an eye.
That Ignis eventually escaped into Den City where he was later captured by Yusaku Fujiki (Playmaker) and Kolter. As he was an AI and an eye at the time, they decided to nickname him "Ai". Ai later reclaimed his body from the Knights of Hanoi after Playmaker defeated Varis.