Blue gives you extra turns, card draw like an UNO player, and the dreaded Counter magic
With strategic gameplay, gorgeous artwork, and the chance to duel it out in a land filled with magical creatures, it's easy to see why
Ongoing Scheme (An ongoing scheme remains face up until it's abandoned.) Creatures you control get +2/+2 and have fear
Faceless Haven is essentially worth splashing for in every monocolor aggro deck, and the Battle for Zendikar cycle of Shambling Vents / Needle Spires / Hissing Quagmire / Wandering Fumarole / Lumbering Falls saw widespread play during its time in the format
Because your commander is so resilient - low cost, only a creature on your turn, and with a built in self-reanimate power, you don't even really need backup reanimators in the deck