Iron Mastiff... you were a relic of a time when this cube was a little less busted. Goodbye old friend. I never cast you once.

During a much more successful second playtest, I had the chance to sit on the outside and take notes on each card's reception and effect on the boardstate. Afterwards I interviewed each player about their decks, cards they liked and avoided, and their feelings about the cube experience. Here's what I found (in order the mainboard changelist):

Yurlok of Scorch Thrash wasn't even played, but its power level precedes it. 1 mana for 6 damage, even if some of that is preventable, would have immediately dominated the board. Deathrite Shaman is the case study for how we know this. It's ramp on turn one, then immediately becomes a threat by draining for 4 consistently. Yurlok does the same thing but ramps you and your teammate while consistently doing 6 damage. Both have been replaced by less powerful but more thematically relevant cards.

Serra Ascendant is generally unfun, it either wins you the game turn one or it's a vanilla 1/1 on turn three. I was also told that white and black creatures generally sucked, so I put a couple on the watch list.
Flux Channeler and Evolution Sage both do nothing when they come down, I needed something that would affect the board when you draw it. Tezzeret's Gambit is a spells for the spells decks, Bloated Contaminator actually threatens the boardstate as a 4/4 for 3 with toxic that also proliferates.

Bone Shards and Bloodchief's Thirst were just in the line of fire as the two worst removal spells in black, and black already had a trillion removal options so it won't miss these. Spawn of Mayhem is like Serra Ascendant except it doesn't win the game. I replaced these three with draw spells because they were needed. Shoutout to Syphon Mind for being funny as shit. Making your teammate discard a card they don't need to draw that extra card is so funny, regardless of the legitimate strategic potential it offers.

Encore cards were questionable in EDH with 3 targets, even moreso in 2HG when you might be spending 8 just to get two of the effect. I left in Amphin Mutineer because it's cute, but Rakshasa Debaser was not that good. Replaced it with Breach the Multiverse which for 7 gets you 4 things without having to attack. Love that, truly.

Red has too many spells payoffs and not enough spells, not enough burn, so I brough Chandra's Ignition (probably an unfun out of nowhere wincon) down a few notches to Electrodominance, Firebrand Archer into an actually useful burn spell in Chain Lightning, and Baird, Agrivian Recruiter into a spell that does things and draws cards.

Last thing, Llanowar Elves just didn't hold up, it had to chump block and it needed more utility. Gilded Goose isn't as consistent as ramp but it can gain life in a stabilized boardstate when you no longer need the ramp and just want the life.

Things to watch moving forward: Golgari graveyard is not a deck. Golgari graveyard is not a deck. Golgari graveyard is not a deck.
Izzet spellslingers has too many slingers and not enough spells.
Orzhov's creatures might need a boost.

The first playtest of this cube was rough. Two of the four players had some very strong criticisms for the choice of inclusions, especially for the cards that only affect one player's battlefield, not both players'.
While I personally think that there's some inter-play between benefiting both boards vs just your board, I do agree that cards like Balmor, Battlemage Captain don't actually have the support to make that inter-play inter-esting.

One thing I noticed is that ninjas were rarely picked and often became the last pick chaff. That said, I think ninjas diversify combat interactions and force blocks, which makes games more interesting. Combined with the battles I'm adding (see below), I think the combat interactions of what to block and when can make ninjas a powerful and fun archetype. I obviously love information games, and I think the information game of drafting this cube is the core tenant I want to shine through. Will be working more around this soon.

Battles are here! And they're very interesting. I'm interested especially in Invasion of Karsus and Invasion of Regatha as kind of diversifying the gameplan of burn decks. By choosing to remove counters from the battle you're essentially gaining your opponent life, but the flipped version will give you even more burn options. Invasion of Fiora is a board wipe and build-around I'm very excited about, and the back-side creates a lot of board/combat tension while drawing you into the tools to win.

While I'm of the opinion that Yurlok of Scorch Thrash will be flat out over-powered and dominate the board whenever it comes down. But more important than its power is that I think it's a pretty uninteresting power (set it down and blast the opponent for 6 every turn). I want Ziatora's Envoy to be a card that complicates combat- either forcing a block or providing card advantage to colors that don't excel in the late game without it. Very likely, I'll end up making this exact exchange later, precisely because Envoy is less powerful but more interesting.