This giant spider appears above Midway Pier.
Assembling the effigy is straightforward. There is a base, a center piece with flat metal bottom that goes into it, legs on each side, and a spring on its butt. The sides go together non-symmetrically. There's a gear connection further forward on one side and further back on the other side. The pieces might float above your head, so remember to look up if you're missing a piece.
Once activated, this guardian is the Midway Pier metalwork above the fair. It creaks to life, and the head glows with 5 large dots. The center dot will light up a laser sight and then produce a powerful beam shot once its aim settles on a pillar. It's confusing to see exactly where the spider is moving, due to the complexity of metal beam structures and night-time lighting, but the laser sight is fairly bright and broad. You won't have much time to dodge.
To attack the spider, aim for the glowing eyes.