Any character carrying the Treasury of Proteus will have it polymorph contents and absorb curses. For Pirates only, even when it's cursed, it affects luck like a noncursed luckstone. For non-Pirates, it becomes cursed outright when it absorbs a curse, even if it was blessed. So Pirates don't need to worry about it becoming cursed, but they have an easier time keeping it blessed if they want to.
Any character carrying the Treasury of Proteus will have it polymorph contents and absorb curses. For Pirates only, even when it's cursed, it affects luck like a noncursed luckstone. For non-Pirates, it becomes cursed outright when it absorbs a curse, even if it was blessed. So Pirates don't need to worry about it becoming cursed, but they have an easier time keeping it blessed if they want to.