It seems to be a nonstandard item, so it is unlikely that anyone except your DM will be able to provide you with a definitive solution. That said, one thing you can try is to gather information - ask priests, wizards, bards, sages, etc. if they know or have heard of any similar items (turning into a raven or the purple
ooze may be a significant symptom), and if so, how it can be countered....