The Crossbow will lock on to any hostile mobs it detects while avoiding Creepers, however it will also attack Zombie Pigmen and Endermen despite not attacking Witches. Because it fires autonomously, you can't control what it will go after.
The Automated Crossbow has one inventory slot for arrows of any type. It can be picked by right-clicking it with a wand. The Crossbow has 10 health and can be destroyed by sources of damage, leaving behind only a few pieces of itself as well as the arrows it was holding. It will consistently drop its Brass Gear, with high chances of at least one Greatwood plank and, more rarely, its Clockwork Mind. It will take around 30 seconds for a Crossbow to regain a full heart of health.
The Automated Crossbow is created at the Arcane Workbench with a Clockwork Mind surrounded by a Brass Gear at the top, a Greatwood plank to each side, a Bow at the top left, an Iron Ingot at the top right, all balanced on two sticks at the bottom corners.