so on the subject of stolen property, i’ve seen various arguments on this point but it is in fact true that inheriting something from a relative, when you know full well that it was stolen, does not make it yours.
this clearly goes doubly so for powerful magical artifacts, and especially for artifacts which are strongly implied to contain part of their creator’s soul!
you can talk about consequences - maybe the artifact in question has benefits for you, maybe you’re not convinced its rightful owners would use it responsibly - but talking about the consequences doesn’t erase the fact that whatever benefits you think you’re getting are achieved through wrongful means.
which is why i, too, think Frodo should have given the One Ring back to Sauron. thief.