For some reason the item “tomb ring” to command skeletons is being listed as necessary equipment for the Cloudrip Commander level, which is supposed to be the first level you use the Boss Star in. I ponied up the 900 gems to buy it, but this seems like a bug / mistake.
I’ve come across a few other levels in which items are allowed that shouldn’t be as well. If there’s a better place to report bugs like this let me know.