As they are obviously not nearly as powerful as a player, they are meant to represent mini-players, complete with their own life pool, a small set of spells and costs
Its important to keep in mind that neither the Executioner nor Despoiler of Souls can block
Of course, the Reanimator player casting this on turn one or two will frequently be bringing back Grave Titan or Archon of Cruelty, while the other player may not even have a creature in their graveyard yet to choose making this one of the very best early game reanimation spells ever
5/5 Speaking of must-answer threats, the second Shredder on the list is just as scary
Flying, protection from spells that are one or more colors, annihilator 6 When Emrakul is put into a graveyard from anywhere, its owner shuffles their graveyard into their library