The difference with Sanctum Prelate is that it can’t be played in Modern since Conspiracy: Take the Crown is not a Modern-legal set. Is this a good card for Legacy? It probably is, as Hatebears may want it. This is a wait and see card, and being a mythic rare, it probably will have a higher price than you may expect. It will definitely see play somewhere, even if it’s just in random Cleric decks in Commander. This is definitely a card I would hold onto a playset of in case it becomes a big deal.