Xerxes IX is one of the “Rare Cats” in Neko Atsume. The only way to get a “Rare Cat” to visit your Neko Atsume yard/home is to place an item that a specific “Rare Cat” likes. In general, you will have to wait a bit between when you place the item and when the cat you wanted to attract appears.
Xerxes IX only likes one item – the Royal Bed. It is a rather glitzy bed that looks quite a bit like a throne. Several other Neko Atsume cats will use the Royal Bed, too.
The Royal Bed is the fanciest bed in the Neko Atsume game. It has a red, quilted, bed with gold edging. It is easy to see why a cat named Xerxes IX will appear after you place the Royal Bed in your yard/home. He wants a throne!
You can buy the Royal Bed in the Neko Atsume Shop. It costs 43 Gold Fish. The description of the Royal Bed is: A gilded, handcrafted, finely upholstered bed fit for catnaps in the lap of luxury.
Xerxes XI wears a little gold crown and wears a fancy blanket.
Other Neko Atusme cats will also use the Royal Bed. Some like it more than others do.