 What's the rarest thing inside the back rooms? Like out of all the entities, the levels, the objects, what is the hardest one to get your hands on? Well, the rarest level is probably level 696, and it's pretty much just a place of repeating parking garage floors that get glitchier and glitchier and more unstable the further you go down. And in the entrance section of the level, it literally says entry to this level happens seemingly at random, so yeah. Then there's object 99, the Hermes device. This is a very rare item that allows the holder to glitch between levels at ease. The only problem is it's pretty much impossible to make. But I think the rarest thing period in the back rooms is entity 666, the happy files virus. The entity can only be encountered on specific computers with a specific file on the desktop. So you probably won't have to encounter one ever if you're lucky.