A kingdom where, if there are multiple princes (princesses can't rule unless they have no siblings), the princes fight to the death in the arena to decide who gets to rule. A simple way to make sure your brother cannot make a bid for the thrown, and keeps the royal blood in one line.
Made from the tears of a bound goddess, this magical wine has the power to charm or dominate any who imbibe even the faintest quantity. Once affected, it remains dormant until the victim hears a special magical phrase, upon which they will be magically bound to the speaker. Enterprising villains could drop this into the water supply of an important city..