Just remember, these are not tournament legal, so they're exactly like MTG Proxies you could make at home, and probably not worth gambling thousands of dollars to obtain.
At the beginning of your upkeep, if there are four or more cards exiled with this artifact, choose one of them at random
If the seller doesnt accept returns, make sure it stays out of your playing deck (or completely get rid of it)
Model of Unity is also an interesting way of manipulating votes, persuading players who voted for your choice with a free scry 2
Of course, you'll want to make sure Blood Hypnotist is accompanied by cards that generate Blood tokens, so this bloodsucker isn't a great candidate for slipping into the decks you already have
Compounding these problems even more is the fact that its in players best interest to buy as many of this product as possible