It allows you to prevent combat damage from one other creature, and if you were the player that creature attacked, you can draw cards based on half the damage it would have dealt
While some characters that didn't get a card at least appear in the artwork of a card, Basch didn't even get this
If you've been itching to say 'no' to your opponents for whatever shenanigans they're planning on doing, you're going to want to build one of these decks
Each different gem corresponds to a different color of mana, so if a player had a rainbow deck with all five, they could unleash an unpredictable, and powerful, strategy of their choice
Where Black Lotus gives you free mana, Ancestral Recall gives you very cheap card draw
Honestly with a resume like that, the choice to max out on Leyline looks sensible