Bestiary

Einhar Frey, first found in Act 2, wants your help capturing beasts to place in his Menagerie. Einhar only wants beasts he feels are "worthy" of the First Ones, so he will only appear when there are beasts with Bestiary mods in the area. These are easily identified by their yellow or red icons on the minimap. For Einhar to capture a beast, you must first weaken it through combat.

Captured beasts are taken by Einhar to the Menagerie. Your Menagerie is shared across all characters in the same league on the same account, much like a Hideout. Other players can enter your Menagerie if you allow it, and you can enter theirs. The Menagerie has a small arena with a stone plate, called the Blood Altar. At the Blood Altar you can perform 'Beastcrafting'. This requires that you select a recipe for which you have the required beasts. Once selected, those beasts will attack you in the arena.

Eventually you may be able to fight one of the four Spirit Beast bosses, each of which can drop their own special set of unique items. These are the pinnacle fights available through Beastcrafting, and may require that you capture particularly rare beasts.