Hallucination

Hallucination is a ghost in the aura list. It has no roll chance and no recorded creator, the wiki labels it a removed aura, and the data here marks it Unobtainable with no tier of rarity to compute against. If you are looking for it as a goal, there is nothing to farm.

What survives is a description of how it looked. The Sol's RNG Wiki says it had a pale, faded blue tone with a transparent ring moving constantly around the player, and its font was Sarpanch. According to the same page, developer xcvbwer123 first showed it in a server together with two other auras, Sirius_unob and Lunatic, and all of them were most likely removed soon after.

The most interesting note is its place in the design history. The wiki says Hallucination was the unfinished version of the obtainable aura Origin, and that it had been planned as the first aura of the Transcendent rarity before the idea was scrapped. If you want the finished concept, Origin is the aura to look up instead.