UnderMine

On Halls of Din 1, you will find a room with a lever. Activate it for a fight against 3 horde waves. You will get a piece of food between each round. As of this writing, you can cheese a bit by quitting the game if you are close to dying and upon restarting, you will just restart the floor. The layout and relic on the floor will always be the same, but the waves of enemies in this battle are not the same each time. If you're lucky, you won't get the wave that has two necromancers and two blackguards. That wave is the worst.

After you win, you'll get a key. Bring this key to the bookshelf behind Arkanos in the hub and you'll gain access to Griswold. He's the proprietor of new familiars.