This seems like a very nice payoff for the various descending strategies which, keep in mind can include self mill, sacrifice, and more Giving something -2/-2 when this enters seems eminently doable, and thats already a good card
Not only do I think this is the most powerful strategy for Xantcha, it's also the most fun and on-theme
In a multiplayer game, if an opponent loses life and later that turn leaves the game, you can cast a spell for its spectacle cost
Monarch is an extremely powerful ability that can be stolen away if you attack the player with it, so becoming the monarch immediately puts a target on your back
That said, we should expect to see more and more Universes Beyond sets as the basis for experimenting with new design space, and as long as they arent irrevocably changing the meta landscape (Im looking at you, The One Ring), Im excited to see them