I was excited to smell this one, as I'm a fan of Imaginary Authors, and these notes (iris in particular) appealed to me.
When I tested it, I was struck by deja vu. It took a few wearings to figure out what other perfume this smells like, but I did finally put my finger on it: Moulin Rouge by Histoires de Parfums.
It is not identical, or even really that similar, but the iris is dominant and common to both. There isn't patchouli in O, Unknown!, as there is in Moulin Rouge. The tea notes here fill that same role, though.
The notes seem clearer in Moulin Rouge, and more "muddied" here. Also, there is a synthetic note that makes me susceptible to a headache in O, Unknown!.
If earthy, dusty perfumes are your thing, I have no doubt you'll enjoy O, Unknown!. I do. I just find it too similar to Moulin Rouge, which I own (and which I enjoy even more) to justify owning both.
I do like this perfume, and though I wouldn't purchase it, I'd wear it occasionally if it were gifted to me.

complex, interesting, kind of sexy and mysterious but still warm. definitely a great unisex scent, i love wearing it and the black tea note is so yummy. this perfume lasts a good while and dries down well to an ambery musk with that hint of black tea.

Scent of the day : O Unknown, by Imaginary Authors

This one opens with what I can only describe as a flowery pine (iris, as it turns out). For all that, this is truly unisex and not at all girly, especially as it dries down to a blend of black tea (lapsang souchong, providing a really earthy note), sandalwood, moss, and musk balsam. It is intriguing, but not in your face, hovering close to the skin. On me, it has a bit of astringent quality, not quite vap-o-rub, but still vaguely can’t-quite-put-your-finger-on-it medicinal.

I'm getting all of the notes listed but I think I solved the ???. It has envelope seal undertones. I can't explain further!