I was at Oblivion Guardians at the Temple of Time, but there was an NPC there, "Strange Mystical chest" or something like that, and under the name it said, "Special shop". So I clicked it, and it teleported me to this plain room that had the chest again. I clicked it, and this time it opened a shop. It didn't have a whole lot, a gaga transformation potion, and some recipes for a few potions, rings, and the reverse bow. I had almost no money on me at the time, so all I was able to afford was a single transformation potion, but I digress.
I've never had this happen before, or even heard of this shop or chest. Is this a common thing?