I think i've run into something that's going to be a big deal in a bit.

The merchant in the sewerpipe shortcut has stopped selling transient curses. Just out of the blue, I bought a couple and the item dissapeared from her sales list. As far as I know, she's the only vendor who sells them. 
 
 
It's not a pressing concern cause I've still got blight town to do, and anything that might branch off of blight town. But eventually I'm going to have to go back into the ghost area, and without the item that lets me fight ghosts I'm going to be in alot of trouble.

I am actually out of curses and she wont sell them to me atm either.. I know there is a dagger that damages ghosts but i have yet to find it or even know where to look, but if i cant find more curses or Get cursed, i am gonna be screwed as for how far i got through that first part, its FULL of them everywhere.

@Ulong: I think it's more of her (I think) running out of stock of said curses than it vanishing entirely. I've bought 5 of the Curse "Potion" thing from the guy at the belltower and he doesn't sell anymore of them.

@Ulong: Probably some other merchant deep within the world. If not, NG+ it. Demon's was pretty nasty about having limited or even missables on a playthrough.

For peeps to avoid this situation, make sure you're in human form while attempting the ruins. You can easily get like, 8 transient curses from killing all the ghosts in that area.

Are ghosts attackable by blue phantoms that you summon, or do they have to use transient curses themselves as well?

This whole transient curse thing confuses me. Is it different from regular curse? Could you not just get cursed on purpose from the frog enemies and kill the ghosts, then just cure normally whenever you feel like it? It seems weird to buy an item that temp curses you when you can get permanently cursed for free and the thing that cures that is cheaper than the temp curse item... Or am I completely off base?

@SuperfluousMoniker: I think the frog curse is different, it instantly kills you and you have 1/2 hp until you are cured