Ok guys hear me out....
Academy Rector and Arena Rector:
They sac to the new White Flare at instant speed as a cost,
You can make them uncounterable via Cavern of Souls,
And grab REALLY powerful permanents like Overwhelming Splendor or Ugin, the Spirit Dragon as quickly as turn 1.
That's pretty cool, and there are a bunch of ways you could build these things...
BUT FURTHERMORE
Restore Balance.
This effect is super busted and can wipe all of your opponent's resources in one shot. Restore Balance combos with Greater Gargadon to sac all your lands and MLD/wrath/mindtwist your opponent. I mean, come on. You know Balance. Banned in Legacy restricted in Vintage, this is Omega level stuff. You need to play it in a cascade or other 'cheaty' shell like Beseech the Mirror to reliably cast the balance. This used to be a pretty fun deck in modern, the cascade shell with Spirit Guide ramp and instant speed payoff through Violent Outburst, plus bombs like Nahiri, the Harbinger and As Foretold, it could do some really cheeky plays and was just an incredibly interactive and fun deck to play in modern. That was my favorite deck for a long time but the bans of SSG and Outburst have rendered the cascade version pretty unplayable now. But who cares about any of that anyway, we're gonna play some Legacy, baby!
So, how do balance and rectors play together?
Primarily, the rector payoffs stick around through a balance, and gargadon cheaply sacs rectors and can't really be interacted with because of suspend. This gives us 9 un-interactable sac outlets (4 Garg 4 Flare and Phyrexian Tower, 12 if you count Urza's Cave, and 16 with Fury.) So we have lots of sac outlets and lots of rectors, we can make the whole thing uncounterable, and that's theoretically why the deck is strong.
The main downside here is that rectors cost 4 mana and this is slower than most other 2 card combos in the format. Sometimes too slow, and the cascade shell does limit available fast mana options. Balance works well here as a tactical sweeper, buying time to assemble the combo. Alternatively, a fast rector into a lock piece like Overwhelming Splendor can also stall/imprison your opponent and make your followup plays e.g. Yorion much more lethal. Rectors also work great as blockers/deterrents even if you don't have a way to immediately sac them. A lot of the combo-enabling cards such as Fury and Flare of Fortitude, or The One Ring, also serve as stop-gap removal or protection. So each side of the deck can act flexibly as both stall and finisher. Remember that Greater Gargadon comes out of suspend as a HASTY 9/7 with flash and can easily close out games. Many players don't even realize it gets haste because nobody pays attention to niche rules for barely played mechanics from 18 years ago.
Another strength I found with the deck is that the rector and balance strategies work along different angles, rectors are stopped by graveyard or search hate and balance is stopped by Rule of Law effects and Chalice of the Void. Because both strats can win on their own, our opponent will need both graveyard AND cascade hate to shut us down, and on top of that we can still field a decent board with evoke creatures and Yorion.
Incidentally, both strategies also benefit from a larger deck size, making it less likely to draw your unplayable balance or rector targets. And regarding those uncastable bombs rotting in your hand, this can actually pay off by rectoring up Omniscience and casting them+any extra rectors for free followed up by a hardcast balance with 1 card left in hand, and that card is Dovescape. This can all happen turn 2 pretty easily and these sort of lines represent the upper end of the deck's power. Valakut Awakening
also helps you dig + bottom cards if you really need to put a specific card back in the deck. Rings dig a lot too of course and it's really nice to be able to sac them to the gargadon.
That doesn't cover every angle of play in the deck, but it should give you a good idea of how the deck functions and our general gameplan.
----testing notes/record----
I playtested the list a bit on a certain free client and it did QUITE UNEXPECTEDLY well, scoring wins against a variety of meta decks. The record over the first day of testing was an astonishing 9-2 matches!!!! with losses against mono black saga and a jeskai tempo/control list (not BTB, a brew with Samwise Stouthearted), while we WON OUR MATCHES against affinity, murktide, ninjas, elves, burn, beseech storm, jeskai BTB, cloudpost, and mono R prison!!!!
UPDATE: I did a whole second day of testing, won several more games (wins vs 1 dredge, 1 affinity, 1 mono b saga, 1 burn, 1 infect, 1 ceph bfast, 1 moon stompy, 1 azorius control, 1 show and tell, 1 mono w hatebears, and lost to ruby storm, lost to lands playing the new Sowing Mycospawn, lost to naya initiative, to nic fit, oops all spells, and finally a very tense one to boros painter in g3.)
We also played against UB reanimator twice and lost both of them 1-2, but the games were so close! I think the deck can beat reanimator, it did beat reanimator! In g1 vs the first opponent I drew the nuts and won on turn 2 with rector>omniscience>another rector and recruiter and fury, and in the other match won g2 with just LotV+yorion. I'm leaning on the leylines pretty heavily but another option would be to sideboard something like a Containment Priest to hit as a cascade target.
I also completely stomped one a guy who thought 'MH3 Legacy 2/3' meant, 'bring your mono white kitchen table angels deck' And it was sad, so we're not going to count that one.
The record for day 2 is 10-8 and total completed matches 19-10. I may continue tracking this totals and keep it updated, for science!. Though I might not because it was a big pain going through all the replays to verify. Keep in mind this is in a crazy ****atrice meta as well. In almost all the wins, I managed to do 'THE THING' before they could kill me or execute their own combo, often on turn 2-3, then proceeded to steal their creatures with Bolas or wipe with Ugin, or lock them out with Splendor. Many games also involved resolving balance, it saved me from aggro and it was an instant game-ender more than once!
Notes regarding the stats: As a rule I DID count several match wins where opponents lost g1 and then quit. no goldfish (1 of affinity, murktide, cloudpost, 1 of burn, cb, s&t. I actually played against the show and tell guy again later, beat him in g1 again and he ragequit a 2nd time and blocked me, so maybe that counts as a full match after all). I DID NOT count 3 losses where the opponent beat me and left after g1 (mono b reanimator, murktide, and what I can only describe as Boomer Jund). Just so you know. I have the replays for EVERY game referenced here saved so if anybody wants to see a specific matchup, let me know and I can send them to you!
Update 2: I logged on for a single game today and it ended up being our first time going up against beans. They were a 60 card bant miracles list, and we absolutely smashed them 2-0 winning g1 with a Dovescape, Omniscience, and finally a third rector for Ugin sealed it. Though I might have misplayed a bit with the Omnisience since I almost lost to their dove army, instead of omni I could have grabbed Sandwurm Convergence. Then we won g2 handily with an uncounterable rector+flare into Kaya, Intangible Slayer on turn 3. Which brings the record to a nice, round 20-10. HOT!
----conclusion----
To wrap things, I think that these strategies actually synergize really well and might be legacy playable. I loved Cascade/Balance in modern, the deck was pretty competitive in its heyday (though not played much), but it never had the tools it needed to work in legacy. Modern used to be a much faster and more combo-oriented format, too! I had thought about rectors and balance and gargadon before, but it was the loss of the modern deck and the spoilering of the new Flares that made me really want to build this. In practice I thought the rector and balance bits complimented eachother really well, each playing to both the strengths and weaknesses of the other. There were some frustrating moments and losses where we were too slow, couldn't find the Cavern of Souls when we needed it, got Oppo'd, but there were just as many games where we stuck a turn 2 uncounterable Ugin and won, and even more games where we did it turn 4 or 5 or even turn 10 with 3 life left and still won.
Anyways, just a crazy meme idea but it totally blew me away with the performance. It was tons of fun, effective, and pretty inexpensive by legacy standards, I think (about $2k and that's almost all in the 4 duals), maybe this crazy science experiment could be an actual deck lol. Is cascade balance it the best shell for rectors in legacy? No clue, but it IS powerful as hell against some of the best decks in the meta--as is evidenced by our 19-10 winrate!
----card considerations----
Like I mentioned before, I'd like to try Containment Priest in the board as an alternate cascade hit vs graveyard decks where the effectiveness of balance is limited. I also considered Crashing Footfalls as an alternate payoff, but I think it's rare that this will be better than balance in the deck. Still, could be a nice juke option for just 1-2 slots. Gaddock Teeg and Angel's Grace are similar considerations. Adipose Offspring would allow Recruiter of the Guard to find a sac outlet for 2 extra mana, I think I will actually have to try and play this just for how cheeky this card is. But I have a pretty high density of sac cards so I don't know if it's necessarily worth the slot. Also considering Dosan the Falling Leaf for counter-heavy matchups but I cut it because I think an uncounterable rector is usually enough to win the game, and Dosan is really only good with Cavern of Souls out anyways. Ricochet Trap is another option. I've thought of moving Dovescape to the sideboard as it feels like the most situational enchantment, but I like how it plays with Sandwurm Convergence and Ugin, and it's very good against beans and also storm decks which make up a decent part of the meta. I could also board the sandwurms, but this card is our 'hitter' to grab off academy rector, without it we can find ourselves with no way to pressure from an academy, and it's a great defensive card vs affinity and murktide as well. I also like having locks with wurm+dove, as well as ugin+dove, as I mentioned. Boltbender is a spicy tech card to counter Endurance and Surgical Extraction from disrupting our rector plan. It should work in theory but in practice it was a bit too expensive to keep mana up for, so I cut it to try some different sb tech. Endurance was originally a 3-of just for a good defensive body, but I cut it to make room for rings. Pyrokinesis is another card I'd like to find space for a 1/2-of but the space isn't there. Finally, the big stumper for me is--I want 4 The One Rings, 4 Solitudes, and 4 of each Ley line post-board but there just isn't room for all of it so I'm not quite sure what the correct numbers for each are. Currently it's at 3 Ring, 4 Solitude, 2 Sanctity, 4 Void (cut 1 ring 1 sanctity and 1 FoV to fit teeg + containment priests and the full 4 solitude which is necessary for oppo and other problem creatures. Optimally I would have 2 Priests sb but I cut 1 and moved a solitude to fit the Adipose Offspring just because this card is swag)
So this last section is probably where I'm most interested in getting feedback because those are the remaining deckbuilding questions I am trying to figure out, or if anyone has any card recommendations I've completely overlooked I'd love to hear those too! If anyone actually read any of this, thanks for checking it out and hopefully you will have some fun testing out the list or trying your own Rector brews!