For X and two Black mana, you get a sorcery that makes each opponent lose X life, and you then gain life equal to the amount lost because of the card
Do it enough times and youll eventually have enough cards to tool around with making your own decks to try out in the games friendly mode, Quick Start
Since the permanent is a creature and not a planeswalker, it can't be chosen as a target when your opponent declares attackers, and it won't leave the battlefield if it runs out of loyalty counters
Both of Yunas abilities were designed specifically to interact with summons, especially expensive ones like Bahamut and Knights of the Round
The Banyan Tree / The Great Henge (TLE) $47 Initially, I thought that this cards price was high because it was a special Avatar reprint, but boy, was I mistaken
The best part is that it scales with what you might be doing anyway, or just with the game itself