From the publisher's website
Due to the popularity of our Monster Tile Set, we have made an expansion! Players asked for more Huge and Medium creature tiles, and we listened.
Monster Tiles are lightweight, store in very little space, durable, and quick to set up. When you're done, just scoop them into a box or bag and you're ready to go. Perfect for convention gaming!
This expansion contains:
12x Medium Tiles (labeled 13-24)
6x Huge Tiles (labeled 3-6)