No

Graaz (C): lolnope. Colorless commanders are basically nonstarters in Historic Brawl, especially when they're as goofy as this. The cards within each tier aren't in any particular order, but if they were, Graaz would be dead last.

Jace (U): Mill isn't really viable in HB unless you're combo-milling your opponent's entire deck in one fell swoop. I think Jace could be a decent card in the 99 just for the card draw, but as a commander, no thanks.

Melira (GW): I don't see how you build a deck around being resistant (not even immune!) to poison.

Ria Ivor (WB): This card just kinda sucks, sorry!

Slobad (R): You don't want to be playing expensive artifacts solely to sacrifice them to play, presumably, even more expensive artifacts. Maybe sacrificing middling mana rocks into huge finishers is a thing, but Slobad would need to be quite a bit cheaper to justify that, I think. (It's possible that Slobad enables some sort of degenerate combo I haven't spotted.)

Tekuthal (U): There's not enough proliferate available within mono-blue to make Tekuthal work - only sixteen cards besides Tekuthal himself, and that's if you include the really bad ones like Gitaxian Anatomist.

Venser (UB): Everything I said about Tekuthal applies here too. Venser fares slightly better for being in a second colour, but the payoff is a lot weaker.

Borderline

Atraxa (GWUB): I'm a little surprised to find myself putting Atraxa this low, but then I think about the kind of deck she enables: loose many-coloured goodstuff piles. If you're playing that, you're probably already running Jodah or Niv-Mizzet, both of which are cheaper and give you the full five colours (Atraxa is missing red).

Ezuri (GU): I could be wrong here, but my instinct is that seven mana (and you really do want to wait until you have the full seven) is too much for this effect. That said, Ezuri's a potential superfriends commander, and I don't think we have one of those in this colour combination yet.

Geth (B): Everything Geth does, Muldrotha mostly does better - she gives you more colours, lets you recur all permanent types, doesn't debuff your board, and doesn't exile your reanimated creatures when they die. I guess the theoretical use case is to discard something massive and reanimate it for cheap, but that seems tricky to pull off in mono-black.

Karumonix (B): There are a surprising number of mono-black Rats in Historic, but a lot of them aren't very good, and they're especially short on evasion, which is what you'd need to make a poison-centric Karumonix deck work well. Keep an eye on this one - it may become more viable with time as more Rats are released.

Kethek (BR): This breaks the cardinal rule of Polymorph effect abuse in that it can't turn a worthless token into a game-ending bomb. Sacrificing something to get something less valuable isn't likely to be worthwhile unless you have really good death triggers.

Koth (R): Much as it pains me to put my favourite planeswalker here, Koth is outclassed in the field of Big Red midrange / control commanders. He makes a great addition to the 99 under Sarkhan, or Tibalt, or one of the seven gajillion Chandras, but he doesn't bring anything new enough to the table to make him stand out as a commander in his own right.

Nahiri (RW): Decently strong card, but I don't know where she fits. Her temporary reanimation looks compelling, and could have combo applications, but her plus abilities are awkward, especially her first one, which encourages defensive play in a colour pair that's normally all about aggro.

Ovika (UR): Seven mana is always a big ask for a commander, but it's especially so on a commander without green. By the time you get Ovika down, your opponent can very likely pay for the ward cost. I can see some possible applications for this card in decks that lean hard on artifact synergy, but it has stiff competition there within its colours in Galazeth and BRO!Saheeli.

Skrelv (W): I think you basically have to disregard the toxic on this card and judge it on the last ability, which does have merit - it's not far off Mother of Runes, and Mother of Runes (aka Mom) is an extremely good Magic card. Maybe some very low-to-the-ground white decks want to always have a Mom on turn one, but those decks tend towards multiple small creatures, which plays against Skrelv only targeting one thing at a time.

The Eternal Wanderer (W): I don't know. Her abilities feel underwhelming to me for six mana. There's been some noise about a flicker-type deck that exploits her +1, but as a flicker commander she's competing with Emiel and Yorion, both of which bring improved efficiency and extra colours to the table.

Vraan (B): This effect is powerful, but only triggering once per turn makes it compare unfavourably to other black death-trigger legends like Elenda, Judith, and Elas il-Kor, all of which also give you more colours. Even within mono-black, Vraan is arguably outclassed as an aristocrats commander within this expansion; see Drivnod under "Hell Yes".

Zopandrel (G): This effect strikes me as rather win-more - your already-big creatures are now even bigger - and there's anti-synergy with her activated ability which wants you to sacrifice those enormous creatures. And she doesn't even have trample! I think you could be doing scarier things than this with seven mana in green, like Old Gnawbone, either version of Vorinclex, or see Nissa under "Yes".

Yes

Elesh Norn (W): This is the "Yes" that's closest to a "Hell Yes". Panharmommycon (I'm sorry but I heard that nickname on a podcast and now you have to hear it too) is undoubtedly very strong, and compares pretty respectably to her obvious rival Yarok - the latter may have more colours, but the former has better flicker effects, is easier to cast, and hoses your opponent hard. That said, you do lose out on green ramp compared to Yarok, which, at five mana in a colour that usually prefers a lower curve, could hurt.

Glissa (BG): Glissa's not very synergistic but she's extremely strong. First strike plus deathtouch amounts to "win almost all combats". Black-green goodstuff midrange decks who just want a reliably castable value machine will definitely have their eye on her.

Jor Kadeen (RW): There are a lot of Equipment-themed commanders in red, white, and red-white. The best two are Akiri and Bruenor; Jor Kadeen is mostly an upgrade over Akiri, but Bruenor's free equip ability is hard to beat. I think they lean towards different kinds of Equipment decks, with Bruenor wanting to stack up individual heavy hitters on single creatures and Jor Kadeen leaning towards multiple smaller Equipment on multiple attackers.

Kaito (UB): Good grief does Kaito have a lot of words on him. Kaito's synergy factor isn't as high as some others in this category, but he is extremely flexible - it's not hard to use his passive ability to bounce something you wanted to recast anyway and then draw two cards, or lock down your opponent's two best creatures, or keep stalling them with annoying Drones. He kind of reminds me of Krydle, in that he supports a small-creature "saboteur" strategy, but I think Kaito offers a better value package overall and doesn't compete with your actual saboteurs.

Kaya (WB): I know I've been harping on about seven mana being a lot for a commander, but Kaya is one of a kind: she's a planeswalker with hexproof, making her much harder to kill, who is very good at protecting both you and herself while draining out your opponent. Do not underestimate a six-point lifeswing every turn, or how difficult it is to kill a 6-loyalty planeswalker (8 if you plus her right away!) when you can't cheat with removal spells.

Kemba (W): There are a lot of Equipment-themed commanders in red, white, and red-white... hold on, haven't we been here before? Kemba is a pretty tentative "Yes" because I'm quite lukewarm on his anthem ability - if you're already giving your creatures big Equipment, an extra +1/+1 doesn't mean as much. However, being able to make a 2/2 for five mana as many times as you can afford, and even give it a Blackblade Reforged or Helm of the Host or something for free, is definitely not nothing.

Lukka (RG): With one ability that generates mana and another that deals damage based on your creatures, Lukka reads to me a lot like WAR!Domri, who sees respectable amounts of play helming red-green stompy decks - and Domri can't make 3/3s whenever he feels like it. The kill ability is more expensive as a tradeoff, but Lukka still feels efficient and powerful enough as an overall package to be worthy.

Malcator (WU): Three sounds like a lot, but between tokens, artifact lands, and cheap artifacts like Spellbombs, I suspect Malcator's condition is easier to hit than it might seem. He faces obvious comparisons to Urza, Prince of Kroog, but Malcator comes down a turn earlier, which definitely isn't nothing, and leaves more lingering value if he gets killed. I think both have their place, and they play great together.

Migloz (RG): No real synergy here, Migloz is just an amazingly good deal for three mana. Like Glissa, he's probably best used in a deck that just wants a consistent heavy hitter. In isolation, Migloz is one of the best things a red-green deck can do with three mana, and a lot of players will be happy to just do that every game.

Nissa (G): People have been telling me that Nissa can't compete. That she's worse than Wrenn and Seven. I ask you, friends and allies, is Wrenn and Seven's giant token a plus ability? I rest my case. (Nissa's -1 might secretly be her best ability; it will probably kill a lot of otherwise game-ending bombs.)

Solphim (R): Damage multiplier effects like this often face the challenge that they're rarely more efficient than just playing more burn spells, but they're a lot better attached to creatures. Torbran is the current marquee mono-red damage scaler, and he's really good, but Solphim suits a different kind of deck - rather than low-curve aggro, Solphim wants to be doubling high-X Banefires and the like.

Thrun (G): I think this card is wildly underrated. Thrun's big draw is being extremely hard to kill, and when I think hard-to-kill creatures, I think Voltron - stacking up Auras and Equipment galore onto Thrun and making Big Swings. This is a niche that's not really covered in HB at the moment, and, in the absence of any creature commanders with true hexproof, Thrun's almost-hexproof might still be enough. Granted, he's vulnerable to wraths, but that's what protection spells are for, right?

Tyvar (G): Tyvar is this set's most powerful planeswalker... in a very specific context. Basically, any Elves deck that's currently running one of the black-green Elf commanders (King Harald or Tyvar's other card from Kaldheim) should seriously consider switching to the new Tyvar. Every one of his abilities is an absolute house in Elves - his passive lets mana dorks pay for each other in one explosive burst, his plus gets more use out of your big-mana creatures, and his minus can reanimate an Elvish Warmaster or Allosaurus Shepherd to give your team extra bite, all at a shockingly affordable three mana. The only real strike against him is that, unlike KLD!Tyvar and Freyalise, he doesn't buff your team's power - but you've got other ways of doing that.

Unctus (U): Unctus has obvious artifact creature synergies, but in that respect he's outclassed by Urza, Prince of Kroog. I think his best home might actually be in a blue aggro / "Flying Men" deck with lots of cheap evasive creatures, with his looting ability providing a steady stream of value and the ability to turn spare pips of blue mana into extra points of damage. I can't really think of another commander that supports this right now, and I'm intrigued to find out whether it works!

Vraska (B): What Big Chandra is to mono-red, I think Vraska has the potential to be for mono-black. A lot of black cards play with counters of various kinds, and proliferating (and drawing a card!) every turn can power up those cards while also increasing Vraska's own loyalty. She doesn't have quite the same inevitability as Chandra, but her removal mode is stronger, and her ultimate puts your opponent one proliferate away from death in a way that's similarly difficult to avert.

Hell Yes

Drivnod (B): This is our ~~first~~ second ever "Deatharmonicon" effect (I forgot about Teysa initially, that's what I get for writing this whole thing in two hours with no editing pass), and the card it's attached to is an absolute stormer. Double up your Blood Artist, your Pitiless Plunderer, your Massacre Wurm, all on a card that's scarily easy to make indestructible if you have creatures in your graveyard - which any deck playing Drivnod will very likely have. Combine that with a freakishly good statline for his mana cost (8 power!) and I expect Drivnod to see substantial play.

Mondrak (W): This is Anointed Procession, one of the most exploitable enchantments ever created, on a 4/4 stick. Two of the millions of extra tokens Mondrak creates are a trifling cost to make her indestructible, too. Chatterfang, her closest competition, is in different, worse colours for tokens. Brace yourself, you're going to see a lot of this one.