Help me make cuts. Stop making me add things.
That's a crying emoji. I went over the creatures once and didn't get to noncreatures tonight. White 4s were a particular issue.
Some Cuts:
I've run and cut this card before. I think a graveyard nuke on a flier might be a little strong in a format with a heavy graveyard element.
This is one of the worst "Blink on a Stick" creatures. I think if you're cutting White 4s, this is one to consider. If you
really need another blink on a stick for white, swap this with
Whispweaver Angel instead. That card blinks and can actually be a reasonable finisher in it's own right.
While I like this card, "Golem Tribal" isn't really a thing in your cube and could be a confusing signal to drafters. While this card is
Fine, I don' t think you need it, especially if you're looking to free up White four slots.
This card is arguably worse than Master Splicer, although it does have a few more synergies which could maybe make it desirable. A 4/3 or a 2/1 with two 1/1s just doesn't seem all that good without abundant ways to abuse it.
Having played this card with an Enchantment, Artifact, and Graveyard deck in the same Cube before, I can say from experience that this card is not good very often. Your cube doesn't really have the level of artifact or enchantment support for this card to do much of anything, so I see it as an easy cut.
I've played this card a ton on Arena in Brawl (a format where opponents casting things from zones other than their hand comes up quite often), and it was trash. As it turns out, discarding cards for unblockability on a 2/1 is pretty bad. I don't think this helps support ninjas particularly well, because you can't get the card draw after the fact, and it's not in a great color for madness. This card just isn't good.
You've got more than enough 1-drops for true aggro decks to function, and this card is one of the worst and the least fun. I'd cut this.
It's not uncommon for this card to be a 2/5 or worse. While I think this card is cool in extremely low power environments, yours seems a little too high for this card to be desirable, even with the enters the battlefield ability.
Satyr Wayfinder this is not!
I found this card to be thuroughly annoying in retail limited. It either immediately died to removal or just won the game. The lifelink makes it impossible to race against and the boast ability means it can tighten the grip of a player who is ahead, especially if they are in a go-wide strategy.
I'm not sure this kills enough things consistently enough to be worth a slot. While this card has a reasonably high ceiling, I think it's floor and average case are low enough where it would be worth cutting if you needed a slot.
This just seems like the worst cantrip ever. Would you cube with
Slip through Space? If not, I would cut this.
This card is either oppressive or terrible; it's never "just ok." I'd highly recommend removing it from the cube.
This card just seems so much better than all of your other red cards. It doesn't really demand synergy and yet can provide huge amounts of value. While I don't think this card is broken in your Cube, I think it's going to lead to a lot of feel-bads unless you raise the power level of the environment.
I don't think a 5/5 Swampwalk with a twisted
Staff of the Death Magus ability is really worth the investment of playing a third color for. I can totally see keeping this card for "flavor" purposes in a Black Cube, but I have a feeling it might warm sideboards more often than is entirely desirable for a card.
This card is either not getting cast or just says "7 Mana: Win the Game." I don't believe it has desirable play patterns in 1v1 Magic.
Blink effects that aren't attached to permanents or cost more than one mana to use are often mediocre. When you lose the element of surprise with a blink like this, it becomes a terrible rate to reset an ETB because the opponent will wait to use their removal until you're tapped out. While this card has a tiny bit of value as wrath protection, I think it is an easy cut you won't miss. I think this card was even bad when Grillo played it, and it only earned it's spot by being a blink enabler that could be recurred by
Auriok Salvagers. You don't really have the support for this, I would suggest you cut it.
Having played 3-mana rocks before, I can definitively say they're not impressive. Even though your format is a little bit slower than many, it's still lean enough where taking turn 3 off to play a mana rock can be a big setback, and there aren't that many cards that make this mana acceleration more meaningful than just curving out. I think a small number of two-mv rocks like the black
Signets or Charcoal Diamond would not cause an imbalance in this format if you
really want mana rocks, but as it stands, I would cut the three-mv rocks.
I would even consider cutting
Bontu's Monument, but that card can actually generate more than one mana per turn if you cast multiple creatures, so it's probably fine. It also is just very on theme for a black cube.
Sacrificing a Creature and tapping a land is not usually worth one life, even if you have cards that care about things dying. This looks terrible next to
Phyrexian Tower.
That's 21 cuts if you take them all out, 20 if you replace Felidar Guardian, and 19 if you leave two of the White 4 drops. This brings your cube size down to 456-458, again depending on what you cut. I hope this helps!