Collecting all 71 cards in the Secluded Springs Set will reward you with a Secluded Springs Suicune Icon
It's an ability that Wizards has returned to on nine cards since 2004, the majority of which have seen significant adoption by the players
Sticking to two colors also makes it slightly easier to establish your land base and more reliably get cards out quickly
Its often the ultimate companion piece for plenty of outstanding partner commanders who can draw into it or cheat it out, and is essentially the final boss of blue magic that can turn every card in your hand into an unstoppable threat
Well, it says that if you spend your mana on an X spell, you get to draw a card and gain life equal to half of X, rounded down
In his Duskmourn: House of Horror Vision Design Handoff: Part 2 article, Rosewater covered this mechanic and the intentions behind it