Layers

Layers cannot be rolled and never had a public chance. The Sol's RNG Wiki describes it as a developer-exclusive aura made for xcvbwer123, and it has since been removed, so the question of how to obtain it has no answer today. Its in-game description is a single casual line about wanting to beat a map.

What people remember is the size. Two huge glowing orbs spin around the player and swap between red and blue on every beat of the song, and each beat also sends out a shock-wave that nudges the player to a slightly different spot. Two rings turn below, and the character hovers far off the ground, a more exaggerated version of the float seen in Chromatic : Exotic. The wiki calls it by far the largest aura in the game.

It did not simply disappear. According to the wiki, the idea was reimagined as Equinox in the Eon 1-6 hotfix update, with a chance of 1 in 2,500,000,000, so anyone interested in the concept should look at that aura instead.