Smiro

:smiro: is a joke that grew into an aura. The wiki says it comes from a running gag in the Sol's RNG community about a developer who mistyped the smirk emoji in a Discord message, and the aura carries the typo as its name, colons included. It is developer-exclusive, was removed, and cannot be rolled, so there is no rarity at all. chumering is listed both as the only known admin to use it and as its creator.

What makes it unusual is how little it does. Equipping it changes nothing about the character apart from its title; the wiki counts it as one of only four auras with no visual effect, the others being Deepwoken, Nothing and Find the probability of this aura. It is also the third with special characters around its name, after Cruel and :Flushed:, and the only non-biome aura with several chat message colours. For a player the practical conclusion is simple: it is a collectible curiosity of the game's history, not something to farm.