"Sure." Pheobe starts picking up the trash, starting closer to the road. While Jake and Fetcher examines the pole, Seymour picks up the first stone.
You realize these 'rock' are actually pieces of clay tablets... and they look pretty old. A red drawing, appearing to be part of a snake, is engraved on it. After a closer look, you notice something black hanging from the bottom. But as you reach for it, you realize it's a shadow. A shadow that's not cast by anything...
"Ah!" Pheobe shouts, pointing at the broken stones. Now flying around you, the one in Seymour hands hovering up to eye level. And as you watch, shadows leak out of them, taking an unusual form.