I disagree with using planeswalker loyalty counters as the same thing as mana. Essentially, you're giving yourself free infinite mana. You sure as hell didn't spend seven posts summoning vampires one at a time. Either stick to mana build-up and actually [i]use[/i] it, or use the loyalty counters alone. Don't blend the two things and mutilate the system into total convenience. Summoning minions to attack giving you mana to use a ridiculously expensive artefact to summon (because ignoring what the rules [i]imply[/i] and used to outright state!) an insanely powerful demon is more or less demanding that we accept that every magic rule is bent to facilitate things being as easy as possible for Sorin! Doesn't need to focus on gathering mana, can do that by attacking; doesn't need to worry about whether the target fits, all targets are equivalent; doesn't need to worry about finite knowledge, he has access to [i]literally every damn card that can be played with black or white mana[/i].