Marionette Apprentice is an undeniable include. I've gone back and forth between Blood Artist, which is the most powerful card, and Zulaport Cutthroat, which is a Human. Neither have quite been there, because it's the kind of secondary effect that is good but not quite useful on its own to justify picking it up mid-draft.
This does everything:
Triggers on artifacts
Human
More reasonable stats
Creates an artifact creature token, a servo to boot!
+1/+1 counters
All it's missing is being a Wizard. While the lack of life gain is a notable reduction in power, the versatility is more than worth it.
--
I've been waiting for this set to drop. The last two Modern Horizons sets were amazing for cube and this one isn't looking any different. It's not just power level, it's the revision of interesting effects that weren't quite up to par. So far I plan to include:
Winter Moon -> Winter Orb was too much, this looks exactly right.
Wight of the Reliquary -> Sacrifice, ramp for midrange and graveyard payoff. It's a zombie, too, and a great fit for Golgari decks.
Flare of Denial -> I needed two counterspells for my cube. I needed a free one to go along with Daze and also an unconditional counter for control decks. However, all the available options had flaws. Force of Will is card disadvantage and uncastable otherwise, Force of Negation doesn't hit creatures and everything else is too demanding or weak. Cancel is reliable enough for control and while sacrificing a non-token creature is a huge limitation, it should be reasonable enough. Strategically interesting, even. I also appreciate that it can be used offensively, which helps both tempo and combo decks.
Flare of Duplication -> I've said this before, but this is the first playable version of this effect. And it's a great one! Copying spells is an interesting ability. At worst, it can copy a bolt to go to the face. At best, it can copy opposing spells or play a key part in combos. I feel it's a staple and people are sleeping on it. There are so many funky plays you can make with this thing, from getting 14 draw triggers from Wheel of Fortune to copying Seething Son for a big play.
Flare of Malice -> The black flare isn't the most interesting, but it seems a good way to slot in a sacrifice effect. I currently run none, if simply because most options don't work in modern environment filled with tokens. Being both free and dodging the chaff seems good enough to try. My hope is that it can work in midrange and control decks. Its price isn't too high to play normally and sacrificing a utility creature seems worth the cost for some tempo.
Warren Soultrader -> I wanted to run another sacrifice outlet, but I never found one as useful as Carrion Feeder or Yawghmoth. Being a 3/3 and not having an activation cost gives me hope. It's a zombie and a wizard, which is fine, though I would have preferred if it were a human wizard instead.
Out of the gate, that's 7 cards that will go in. Currently, I'm dissapointed by 49 cards in my cube, so that's a huge chunk of them that will get fixed with this update. Better than fixed, the effects they'll add are more interesting and varied as well.
This does everything:
Triggers on artifacts
Human
More reasonable stats
Creates an artifact creature token, a servo to boot!
+1/+1 counters
All it's missing is being a Wizard. While the lack of life gain is a notable reduction in power, the versatility is more than worth it.
--
I've been waiting for this set to drop. The last two Modern Horizons sets were amazing for cube and this one isn't looking any different. It's not just power level, it's the revision of interesting effects that weren't quite up to par. So far I plan to include:
Winter Moon -> Winter Orb was too much, this looks exactly right.
Wight of the Reliquary -> Sacrifice, ramp for midrange and graveyard payoff. It's a zombie, too, and a great fit for Golgari decks.
Flare of Denial -> I needed two counterspells for my cube. I needed a free one to go along with Daze and also an unconditional counter for control decks. However, all the available options had flaws. Force of Will is card disadvantage and uncastable otherwise, Force of Negation doesn't hit creatures and everything else is too demanding or weak. Cancel is reliable enough for control and while sacrificing a non-token creature is a huge limitation, it should be reasonable enough. Strategically interesting, even. I also appreciate that it can be used offensively, which helps both tempo and combo decks.
Flare of Duplication -> I've said this before, but this is the first playable version of this effect. And it's a great one! Copying spells is an interesting ability. At worst, it can copy a bolt to go to the face. At best, it can copy opposing spells or play a key part in combos. I feel it's a staple and people are sleeping on it. There are so many funky plays you can make with this thing, from getting 14 draw triggers from Wheel of Fortune to copying Seething Son for a big play.
Flare of Malice -> The black flare isn't the most interesting, but it seems a good way to slot in a sacrifice effect. I currently run none, if simply because most options don't work in modern environment filled with tokens. Being both free and dodging the chaff seems good enough to try. My hope is that it can work in midrange and control decks. Its price isn't too high to play normally and sacrificing a utility creature seems worth the cost for some tempo.
Warren Soultrader -> I wanted to run another sacrifice outlet, but I never found one as useful as Carrion Feeder or Yawghmoth. Being a 3/3 and not having an activation cost gives me hope. It's a zombie and a wizard, which is fine, though I would have preferred if it were a human wizard instead.
Out of the gate, that's 7 cards that will go in. Currently, I'm dissapointed by 49 cards in my cube, so that's a huge chunk of them that will get fixed with this update. Better than fixed, the effects they'll add are more interesting and varied as well.
It's a common too! 
