A couple of pictures of a cup fungus from earlier this spring.
Gaze into the inky depths...
You are feeling sleepy, very sleepy...
I believe this is The Devil's Urn, Urnula craterium. At least according to the most entertaining key you'll ever see.
So, The Devil's Urn... the Stephen King of fungi?
There are possibly more suitable candidates for that title:
Bleeding Heart Mycena
Trumpet of Death
Dead Man's Fingers
I found this link about mushroom poisoning in general and the Death Cap mushroom in particular.
The page itself is interesting, but so are the google ads. The first one fits: Morel mushroom hunting. Sure. The next one though, is Hats and Caps for Men. Hmm. Then you have Death Indemnity Coverage. Kind of drives home the whole "world's most dangerous mushroom" idea.