I've managed to make it to Floor 15 at least 3-4 times since the Crownstar Addendum's excessive spawning was fixed, and have never found one since. I do believe that it was changed to include (special="1"), which would effectively make the item never spawn within the dungeon(Just like the magical badass jacket). I'm wondering if it is possible to even see this item in the game(seeing how it doesn't spawn in the dungeon). I'm also wondering if it's craftable or is a guaranteed spawn in a specific unique room, because if it is neither, then I would think that it's completely unobtainable. I was going to reply in the 1.0.10 Feedback thread about this(where the special="1" suggestion came from), but sadly it's locked.
It appears to be unobtainable indeed, there's no room with one in it. I think items with special='1' can still be obtained through randomized artifacts but I'm not certain.
I just found out that special="1" makes the item only appear once per floor, and craftoutput="1" makes the item never spawn at all. Still, even with special="1" alone there is probably a chance that it would not spawn at all.
Yeah, I never drink fountains. Not because of the Acid, but because of the "you feel stupid"(I think it gives lingering dullness?) debuff that insults my intellectual pride. Edit: Besides, I've seen way more Time Lord Scarves from the fountain than anything else, and never had a Crownstar drop from a fountain before. As for ADOM(off topic), One of the first 2-3 times drinking a fountain gave me Fate Smiles on my Paladin.
