Deckbuilding has no clear favorite concept emerging from the first six boosters, but as the two candidate decks have practically no overlap in the cardpool I'll just build both.
The first idea is a GW deck with
- lots of (well, seven...) Elves but limited synergy (only Immaculate Magistrate really benefits from many other Elves in play, and Elvish Harbinger can find it
- Tromp the Domains as a strong reason to go green, although a two color deck isn't ideal
- the combo of Concerted Effort and Crash the Ramparts as a poor man's DIY Overrun
Here are the cards (the two at the bottom left are sideboard). If you look carefully you will notice that apparently I managed to put two dauntless Cathars into the cube - not so unlikely given that the cube is rather large and keeps growing slowly over the years. I will take one of them out of the cube when I retire this deck.
For mana, I have 13 green and 14 white mqna symbols, with two double-white and one double-green and two green mana dorks, so I'll go for 9 Forest, 8 Plains (unfortunately none of the multi color lands were GW, with most color fixing in BG and thus useless for either deck I'm building).
The other deck is what this cube is best at: a Grixis combination of lots of removal and clunky, expensive, weird creatures. No overwhelming bomb creatures, though, so there is some risk involved with having 10 double-colored cards spread over all Grixis colors. The three cards top right are promising sideboard options. (I added Brutal Expulsion to the sideboard, too, the picture mistakenly shows 24 cards for the main).
I have 9 blue mana symbols (2 double-blue cards), 15 black (5 double-black, incl. a BB Hunted Horror) and 10 red (2 double-red) with only one Jund Panorama to find a Mountain or Swamp. So I will try running 5 Islands, 6 Swamps, 5 Mountains and hope the deck doesn't get color screwed too much.
However, I like that the cube doesn't make it too easy to build overwhelming decks around red or black removal, so it will be interesting to see where the power vs. consistency tension leaves these decks.
A first friendly test match between them ended . In game 1, 1a GW just played lots of creatures and pushed through damage while 1b UBR couldn't find a second Swamp to play its double-black creatures or pump Evernight Shade. in game 2, 1b UBR initially created some pressure but 1a GW reset the game with Magus of the Disk (keeping Oakhame Adversary alive with Turn to Mist) and then once again overwhelmed its opponent with lots of creatures in the air. Some sequencing mistakes and some unlucky draws (no removal for opposing flyers, no Swamps to get Evernight Shade to lethal power) meant defeat for 1b UBR.
