Hmm, I like Niv Mizzet and all but what if he's using this maze to somehow attempt a coup by using the guild champions. How exactly does Ral get his spark, HMM?? My guess is the maze is how Ral gets his spark. I really don't know much about the plot though.
I find it highly likely that this deck will be five color, playing off the "solve the maze" theme. Without knowing the full spoiler for the expansion, it's difficult to say how competitive that will be. But based on the DM prerelease details, it does seem as if Wizards is aiming to enable/encourage 3 to 5 color decks in Standard.
You essentially just repeated what I said in a simpler way.
I see people complaining that Sorin isn't in any of his decks art. When did they spoil all the art for both decks? I know they spoiled a few in the article but if you hover over say, Blightning in the composed decklist it will still show the old art. Basically what I'm getting at is the art we've seen is the art they wanted to show us, who knows how much new art we're getting? The set isn't coming out until the 15th anyway.
I think that it's a possibility the event deck might be five color. I'm unsure if this seems like insinuated knowledge already, but perhaps the one event deck with 10 rares could be all of the champions racing to the implicit maze, and the deck uses all of the gate cards in its land pool. Seems like an outlandish idea, and I doubt they'd put the mythic land in it. Also if my theory holds true (which I doubt it would anyway) then either the champions will all be synergistic which would be lame for 10 differently flavored guilds/ or the deck will just suck. Purely speculation.
You essentially just repeated what I said in a simpler way.