From publisher blurb:
Each release for Crawthorne's Catalog of Creatures for the Pathfinder RPG presents a single, new creature for your Pathfinder RPG game, as presented by the famous and retired monster hunter and adventurer, Lord Crawthorne. Each release presents game stats for the new creature, as well as three adventure ideas to help insert them into your game.
An unusual and diminutive construct, the Ioun Eater is solely motivated by its desire to seek out and swallow ioun stones to bring back to its master. It will go wherever it needs to find them, taking them without pause or permission. As it feasts upon ioun stones, the construct grows, gaining strength. It can also expel an ioun stone it has previously swallowed, transforming the artifact into an explosive attack.