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.
Don't verify based on the ring. Can't see, but a snake skin pattern on the stem is a good indicator of an edible. Never trust an internet ID though. Find a knowledgeable person who can see, feel and smell it first hand.
Yeah I don't plan to risk it. I also rubbed the gills on a paper towel and it stained it green, so I'm pretty sure at this point that it's a green-spored parasol / vomiter.