Almanac Eater is a Merchant NPC.
This NPC was implemented manually by the GMs. Since the Almanac of Gods and Demons could not be deleted, you could have exchanged it to this NPC for a Transform Pill (Ghost), Transform Pill (Scarlet Spook), or a Pupu Coupon. This depended on how the GMs spawn the NPC; it took various forms. The chicken form was its default form.