You can keep looping powerful abilities every turn cycle without ever losing your board
Three of them cost seven mana, which is in the realm of game-winning effects, and the other two are huge X spells
Yes, Zombies are one of the marquee creature types of Magic and just like Elves, Goblins and Humans, their rotten tribe has grown to include any niche effect you can imagine, along with multitudinous powerful lords and tribal payoffs
It also does work in the occasional Mill deck
If the mana cost includes , X is considered to be 0
(To be fair, Cawblade wasn't a true control deck, but it did fall into that role sometimes.) Planeswalkers generally tend to have very powerful abilities that can go a long way toward helping you gain control of the game