More angles here:
I think it might be a green-spored parasol which is poisonous, but it's hard to tell at this stage. Was hoping it's something edible because there's lots of them and they're massive.
Looks like a False Parasol in my eyes, though remote ID is a bit hard of course.
Why? The edible Parasol is usually brown with a dark brown underside, has flakes at the cap and stem, and the ring is detachable.
But don't trust my impression alone please, I'm no ID expert!