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We substitute y = yR + yH, z = zR + zH into our equation, and put all the known information on the left hand side
However, since the printing of Prismatic Ending, Jeskai has come back and established itself as the more popular control variant, as the deck now has access to the two best removal spells in the format, Swords to Plowshares and Prismatic Ending, which means you have enough removal for creature decks and reliable ways to deal with problematic cards like Chalice of the Void and Aether Vial
Later, WotC changed this to a keyword ability called defender, and suddenly a whole world of creatures that werent Walls could not attack
Yeah it leaves a token lying around, but when you're playing in a format with giant dragons and menacing Eldrazi, giving your enemies a 3/3 beast seems like a suitable trade off