I like Mesmeric Fiend quite a bit. Partly though because it's got the O-ring loophole which is relevant in aristocrats. I think I'm in the camp that losing the ability to target creatures is not worth +0/+1 and flying. But I feel like it's probably pretty close.
This is cool but probably a pass for me. It feels a turn slow? Getting the card EOT is pretty much like getting the card next turn unless you are running a bunch of instants. So it seems like a Phyrexian Arena that does more damage to you on average but can also attack. Definitely a good card but not sure I need it. I might be undervaluing the body though.
Gravecrawler is great. Not sure there's much to say. The recursion is easy since black has a lot of playable zombies. 2 power for 1 mana is a required baseline for all-in aggro. And because of the recursion, gravecrawler isn't limited to that one deck. Bloodsoaked Champion might be a little better, but crawler has a cleaner text box which I value.
For those who haven't played with Lake or Nykthos, they work very well together. Get three swamps in play. Next turn, play Lake. Sac two swamps and you have 7 mana on T4. Play 7 mana worth of permanents (5-7 black mana symbols). Next turn, play Nykthos, tap for 5-7 mana with just 3 lands. Turn after, play swamp, sac it to Lake, tap Nykthos for 10+ mana. You are vulnerable to bounce or LD on Lake (and to losing permanents that power Nykthos but lake can mitigate this). But if they don't have the removal, you will have a hard time losing with this much mana. Necropotence and Gary make this strategy even better. Life for cards, and recoup that life with Gary. Aggressive card draws with Necro also ensures you have swamps for Lake sacrifice and permanents to play for Nkythos. Engine is fun to pilot and very powerful.
EDIT: Completely forgot about Death Cloud. That's a key card for mono black. It's a win condition and it does everything you need. Wraths, empties hands, destroys lands. Combos well with a late Nykthos or Lake since you can still operate on 3 lands and get 6+ mana after decimating the board with a big cloud.
Memory Jar for sure (unless you desperately need the sweeper effect). Jar is really powerful even outside storm shells. It's a conditional colorless draw 7 for you / mill 7 for your opponent.
Timely Reinforcements is narrow. More of a sideboard card. I try not to run any of those (or at least limit them to disenchant effects).
I'm not a huge fan of most token producers because it's easy for those to take over games without a critical mass of sweepers. Run too many sweepers though and creature based strategies tend to suffer, and it impacts non-token decks disproportionately to token decks. There's inherent imbalance there which strains the meta so I prefer to manage this by limiting the number of token producers. Bitterblossom is probably my favorite token producer. It's strong but not broken and pushes your deck in specific directions to encourages archetype drafting over general "good stuff" strategies. My least favorite token producers are the one shot army-in-a-can types (Cloudgoat Ranger, etc). I generally run as few of those cards as I can get away with (I have a soft spot for Deranged Hermit though).
I use small wood rectangles for tokens. I used to use circular ones, but rectangles made it easier to track which are tapped.
It boils down to what you want to prioritize. Signal/archetype specific cards or general power cards. There's a balance you probably want to strike in the vast majority of cubes. If everything is just generic high power, archetypes get less defined and deprioritized during drafts. My 2 cents that leads to boring drafts since everything is great in everything and you just sleepwalk to a good deck. Too many archetype support cards though and drafting is narrow and on rails - either you draft X deck or you don't and you wind up with a pile. Somewhere in-between I think is best, where you can't sleepwalk to a good deck and you get rewarded for following signals and drafting around archetypes. Season to taste and group tendencies.
If UR spells is an archetype you are pushing, Treasure Cruise should not be missing from your list IMO. It's simply too good in that deck. It UR spell is not a thing, TC is not critical and there are plenty of draw spells you could be running over it. Run it if you like it, or don't. It doesn't matter. Mystic Confluence should probably be in every high powered cube. It's one of blues best cards. My 2 cents is those cards should not be competing against one another. There are reasons to choose Treasure Cruise and take out Mystic Confluence, but not if you are just running a standard high powered list. You need to be doing something outside the normal design before this makes sense (IMO anyway).
Same for opposition vs cyclonic rift. I think every standard high powered list should probably be running opposition. Card is completely ridiculous power level wise. But again, if you're not red lining your list power level wise, there are plenty of reasons to not run opposition. In fact, if you are running a lower powered or midrange focused cube DO NOT run opposition. It doesn't belong in those lists.
I personally like a lot of other bounce spells over cyclonic rift. Into the Roil is probably the best because it can cantrip later. But Repeal is also good (it's more archetypal IMO). Snap, Vapor Snag and Silent Departure are also good if you are really going hard on tempo. Back to the archetype support versus general power card choices. What do you want to do here? All choices are viable depending on what you are tweaking.
Treasure Cruise is excellent in UR spells matter. Maybe the best card in the deck. Mystic Confluence is just super powerful and goes in all Ux decks no matter what they do. So do you want an archetype signal/support card or a generic great card that is an auto high pick?
Opposition is insanely powerful and a key card (at least over here) in Simic decks. As others have said, it's a build around. Card is broken though and it will ruin games of Magic, so you need a high powered cube to handle it. It's not Sol Ring broken, but basically in the tier right below that and IMO there are legitimate reasons for not wanting to run it in a cube depending on your goals. Cyclonic Rift is decent. Has early value in tempo decks and late it can swing games. The overload is really expensive though and it's really only slam dunk great in board stall type of matchups (so midrangy grind fests mostly).
Murderous Cut is very good. Delve is a powerful mechanic that rewards deck building choices. I'm a pretty big fan and think it's plain great in cube. Murderous Cut is often terminate for 1B and can sometimes be cast late for B. Even at 2B, it's good value being instant and very splashable. Not being able to cast it early is a drawback, but it's a nice design for more midrange focused lists FWIW. I'm not running it in my combo list at present but it's a card that I've considered putting in there and might after I so some more testing. Art on it is pretty sweet too (IMO anyway - I know art is very subjective).
As I've maintained mostly retro oriented lists, I've not had to cut nearly as many sacred cows as others have. If I ever did make a fully modernized cube, the hardest cut for me would probably be Genesis. I love that card to pieces and it's too slow for higher powered lists now.
FWIW, I also didn't really care for Grenzo, Dungeon Warden when I tested it. The mana sink is powerful but random. I ran it in a cube with a strong +1/+1 counter theme too but the support for that in RB is poor and so it never really worked in that capacity. So much like calibretto, Grenzo never really found a following. I cut it and haven't looked back.
All that said, many cards we discuss in these threads get minimal time to shine in our cubes because of all the new cubeable cards we are getting set to set. It's a good problem to have (lots of choices) but it also means really good cards - some with staple potential - can easily just fall off everyone's radar and never get the spotlight they deserve. I don't think Grenzo is one of those, but I also can't say for certain it's not.
I never tested Vial Smasher The Fierce but it reviewed well and I can see it being powerful in the right deck. I also like Olivia Voldaren. The nice thing about Oliva is she's a card you are not unhappy running in pretty much any RB deck. She's best in midrange/control but her abilities can take over a game and having that on a 4 drop that swings for 3 flying damage is just plain useful. Falkenrath Aristocrat is the most powerful of all the cards discussed though and if RB is mostly aggressive it's the one I'd play assuming you aren't already.
Ice Storm is cool. Green Stone Rain is a nice card in aggressive decks. As I run some bounce lands, land destruction can be very powerful in my meta. I do run more fixing than most cubes though, so the power of LD is not super powerful across the board. I'm not running stone rain or ice storm mainly due to space but also because the effect is a bit narrow outside build-around type cards (Wildfire) or as silver bullets (punish 3+ color decks with loose mana).
I had to google storm scale. Had no idea people were tracking this. Neato. I love Landfall. I guess it's a 3 which is good for me since I'd like more cards with that keyword.
Fire Imp is ok. Mini flame tongue has its uses. I don't think red really needs it though.
I'm not a huge fan of foils though some do look great. I have a foil promo necro and it's gorgeous. I like old frame va new as a general rule. Black border over white. Non-foil except in rare cases. If a version has easier to read or more accurate text, I'll often prioritize based on that over other considerations. So I guess its case by case.
Hedron Crab is decent in self mill strategies. I wasn't in love with it when I ran it but it isn't awful. In my experience, relying on it to mill your opponent was always a losing strategy though. It really was only useful in UB graveyard/delve decks.
I think the better card is Dakra Mystic. It's mana intensive but it also creates really interesting lines of play and can do a number on your opponent's draws. This is not a card for high powered lists since it's a bit slow, but if you run a low powered list with a lot of graveyard synergies, Dakra is sweet. With no mana cost on the ability, Dakra would be cube-of-all-sizes in my mind FWIW.
My combo list supports a few infinite combos I think. Palinchron + High Tide / Mirari's Wake (or a lot of land). Zuran Orb + Crucible of Worlds + Fastbond. There are probably others. I try to limit these sorts of things to where you have to assemble them and then have a separate win condition. So storm or infinite mana for an X spell or something. Infinite life doesn't really win you the game and neither does infinite mana if you have nothing to spend it on. My guess is there are more degenerate combos than that in my current list and if my cube were played more often some of them would be exposed and I might end up cutting a few if they were too easy to assemble.
Thraben Inspector is very well designed. Pretty much any white deck is happy to play it. It's especially good in midrange/control - offering an early speed bump and a cantrip later when there's mana (also random synergy with artifacts, tinker etc). But even agro is happy with this card. Particularly good in WW with anthems where it becomes Kird Ape that cantrips later after the wrath hits. I think it goes in cubes of all sizes on power merit unless you have a design reason for excluding it. My 2 cents.
I quit the game shortly after Lorwyn. Mythics and an increasingly unreasonable secondary market just made the game too costly for most of the people I played with. What brought me back was Cube and as far as I'm concerned it's the only version of Magic that is still good.
Here of Bladehold is super powerful. Only cut that if you are looking to de-power (i.e. you are running a lower powered rare list). If you are looking to do that though and wish to keep the aggro support slot, Calciderm is better in that role than exalted angel. If your Wx aggro archetype does not need another white 4, keep exalted angel.
Straight black aggro I don't think is all that good. I prefer more aggro/control decks that play to the color's strengths. So Pox or sacrifice strategies. Abyssal Persecutor, Braids, Cabal Minion, Smokestack, Smallpox, Carrion Feeder, various edict effects. I'm also a big fan of mono black. Gravecrawler and other recursive creatures along with things like Ophiomancer work well here. Key cards for mono black are Lake of the Dead, Nykthos, Shrine to Nyx, Gray Merchant of Asphodel, Necropotence, Geralf's Messenger.
For those who haven't played with Lake or Nykthos, they work very well together. Get three swamps in play. Next turn, play Lake. Sac two swamps and you have 7 mana on T4. Play 7 mana worth of permanents (5-7 black mana symbols). Next turn, play Nykthos, tap for 5-7 mana with just 3 lands. Turn after, play swamp, sac it to Lake, tap Nykthos for 10+ mana. You are vulnerable to bounce or LD on Lake (and to losing permanents that power Nykthos but lake can mitigate this). But if they don't have the removal, you will have a hard time losing with this much mana. Necropotence and Gary make this strategy even better. Life for cards, and recoup that life with Gary. Aggressive card draws with Necro also ensures you have swamps for Lake sacrifice and permanents to play for Nkythos. Engine is fun to pilot and very powerful.
EDIT: Completely forgot about Death Cloud. That's a key card for mono black. It's a win condition and it does everything you need. Wraths, empties hands, destroys lands. Combos well with a late Nykthos or Lake since you can still operate on 3 lands and get 6+ mana after decimating the board with a big cloud.
I'm not a huge fan of most token producers because it's easy for those to take over games without a critical mass of sweepers. Run too many sweepers though and creature based strategies tend to suffer, and it impacts non-token decks disproportionately to token decks. There's inherent imbalance there which strains the meta so I prefer to manage this by limiting the number of token producers. Bitterblossom is probably my favorite token producer. It's strong but not broken and pushes your deck in specific directions to encourages archetype drafting over general "good stuff" strategies. My least favorite token producers are the one shot army-in-a-can types (Cloudgoat Ranger, etc). I generally run as few of those cards as I can get away with (I have a soft spot for Deranged Hermit though).
I use small wood rectangles for tokens. I used to use circular ones, but rectangles made it easier to track which are tapped.
If UR spells is an archetype you are pushing, Treasure Cruise should not be missing from your list IMO. It's simply too good in that deck. It UR spell is not a thing, TC is not critical and there are plenty of draw spells you could be running over it. Run it if you like it, or don't. It doesn't matter. Mystic Confluence should probably be in every high powered cube. It's one of blues best cards. My 2 cents is those cards should not be competing against one another. There are reasons to choose Treasure Cruise and take out Mystic Confluence, but not if you are just running a standard high powered list. You need to be doing something outside the normal design before this makes sense (IMO anyway).
Same for opposition vs cyclonic rift. I think every standard high powered list should probably be running opposition. Card is completely ridiculous power level wise. But again, if you're not red lining your list power level wise, there are plenty of reasons to not run opposition. In fact, if you are running a lower powered or midrange focused cube DO NOT run opposition. It doesn't belong in those lists.
I personally like a lot of other bounce spells over cyclonic rift. Into the Roil is probably the best because it can cantrip later. But Repeal is also good (it's more archetypal IMO). Snap, Vapor Snag and Silent Departure are also good if you are really going hard on tempo. Back to the archetype support versus general power card choices. What do you want to do here? All choices are viable depending on what you are tweaking.
Opposition is insanely powerful and a key card (at least over here) in Simic decks. As others have said, it's a build around. Card is broken though and it will ruin games of Magic, so you need a high powered cube to handle it. It's not Sol Ring broken, but basically in the tier right below that and IMO there are legitimate reasons for not wanting to run it in a cube depending on your goals. Cyclonic Rift is decent. Has early value in tempo decks and late it can swing games. The overload is really expensive though and it's really only slam dunk great in board stall type of matchups (so midrangy grind fests mostly).
As I've maintained mostly retro oriented lists, I've not had to cut nearly as many sacred cows as others have. If I ever did make a fully modernized cube, the hardest cut for me would probably be Genesis. I love that card to pieces and it's too slow for higher powered lists now.
All that said, many cards we discuss in these threads get minimal time to shine in our cubes because of all the new cubeable cards we are getting set to set. It's a good problem to have (lots of choices) but it also means really good cards - some with staple potential - can easily just fall off everyone's radar and never get the spotlight they deserve. I don't think Grenzo is one of those, but I also can't say for certain it's not.
I never tested Vial Smasher The Fierce but it reviewed well and I can see it being powerful in the right deck. I also like Olivia Voldaren. The nice thing about Oliva is she's a card you are not unhappy running in pretty much any RB deck. She's best in midrange/control but her abilities can take over a game and having that on a 4 drop that swings for 3 flying damage is just plain useful. Falkenrath Aristocrat is the most powerful of all the cards discussed though and if RB is mostly aggressive it's the one I'd play assuming you aren't already.
I had to google storm scale. Had no idea people were tracking this. Neato. I love Landfall. I guess it's a 3 which is good for me since I'd like more cards with that keyword.
I'm not a huge fan of foils though some do look great. I have a foil promo necro and it's gorgeous. I like old frame va new as a general rule. Black border over white. Non-foil except in rare cases. If a version has easier to read or more accurate text, I'll often prioritize based on that over other considerations. So I guess its case by case.
I think the better card is Dakra Mystic. It's mana intensive but it also creates really interesting lines of play and can do a number on your opponent's draws. This is not a card for high powered lists since it's a bit slow, but if you run a low powered list with a lot of graveyard synergies, Dakra is sweet. With no mana cost on the ability, Dakra would be cube-of-all-sizes in my mind FWIW.
My combo list supports a few infinite combos I think. Palinchron + High Tide / Mirari's Wake (or a lot of land). Zuran Orb + Crucible of Worlds + Fastbond. There are probably others. I try to limit these sorts of things to where you have to assemble them and then have a separate win condition. So storm or infinite mana for an X spell or something. Infinite life doesn't really win you the game and neither does infinite mana if you have nothing to spend it on. My guess is there are more degenerate combos than that in my current list and if my cube were played more often some of them would be exposed and I might end up cutting a few if they were too easy to assemble.
I quit the game shortly after Lorwyn. Mythics and an increasingly unreasonable secondary market just made the game too costly for most of the people I played with. What brought me back was Cube and as far as I'm concerned it's the only version of Magic that is still good.