The thopterist helps bog down the board so that you can block creatures and buy more time, while also providing you with two more "mana sources" because the thopter tokens can be used for improvising out more cards
Like most Magic: The Gathering cards, the value of Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (Final Fantasy)
It allows your team to get in without worrying about losing them in combat, which can be pretty nice especially if you have other beefy stuff that gets better with trample
Its a reference to The Rack, which damages the opponent if they have two or fewer cards in hand
But the Magic calendar waits for no column, and theres already have a new release on the horizon: Commander 2015 , the latest in Wizards now-annual multiplayer precon series