Chyos
1. when you find the chalice, there is some debate in the party on whether or not it is really cursed.
the obvious way to check is to take it to gwen and have her use her magic to examine it. what with her being the goddess of magic.
she could confirm for you that it is cursed. explain the nature of the curse. and possibly even modify the curse or remove it (maybe leaving a "purified" chalice?).
2. the chalice of fortitude is very clearly making people much stronger (and possibly into some sort of lust vampire) according to all the dialog as well the fact you encountered those semi-immortal warriors trapped in that cave.
when you drink from it, you don't actually get any stronger. your HP/MP and all stats remain exactly the same.