The latest Brick Monsters release is available from drivethrurpg.com. The phantom fungus is a fungus creature. They were created as a low level invisible creature in 3rd edition. Two builds are included as usual. The builds are very different. Even if you don't have all the pieces, the instructions might inspire you to create something with the bricks you own. The mpd file is included to allow you to conveniently order the parts using bricklink.com.