Cool idea fam, are you playtesting it right now?

Coupla ideas I came by while reading:Abrupt Decay----->Beast WithinPreordain/Ponder----->Heroic Intervention

Heroic Intervention + Isochron Scepter is so good, especially with Leo obviously.

Those are some solid suggestions. Ill add them to the maybeboard.

Yes I am testing the deck and its going quite well. Adapting the combo to Leo has been pretty easy since there are so many good cards that draw the entire deck.

I truly adore this build. I love Paradox Engine, which immediately become one of my favourite toys in cedh. I also don't like classic doomsday wins cause building a pile is such a boring and repetetive thing, in fact if you play in the same meta over and over it is quite easy for the opponents to predict and pretend and if anything goes wrong, well you just lose. This deck on the other hand contains everything I love in cedh. I'll keep an eye on this decklist, you have my upvote and attention.

Btw why don't you use Force of Will (not enough blue spells?) or Spell Pierce?

Rarian: Thank you for the kind words bud :-) Force will find itself back in the deck. I cut it in part to see how low I could get the curve for testing purposes. I like spell pierce too but to test new cards its not currently in the list. I have found this to be an effective way to seperate the "wheat from the chaff" when I am tuning a new list.

Tbh even if I run FoW myself in my Leovold midrange list, I do not like it, as a Commander Leovold desperately looks for that card advantage. Everytime I lose those two cards I feel a drawback heavier than it looks from outside. This is my opinion, of course, but it's the first time (maybe) that someone says this about Force of Will in Leovold, and I feel that's true.

Oh perhaps you find these useful: I like to run Geier Reach Sanitarium, and Yavimaya Hollow, Sanitarium is devastating after a weel or after you scout someone with gitaxian probe having a counterspell as only card in his hand, and also to get the cards you want a little bit faster. Hollow is an utility land that perhaps you couldn't be interested in due to the fact that your deck aims to be faster than mine (speed is not exactly an option in my meta that is heavily control and attrition based), but it makes your opponents think more and makes you able to play more aggressively.

thedrawnpain: Your assessment of FOW is not far off the mark. It is a bad card in many ways. For this particular build of Leo its worse than normal since Engine burns through hands so quickly.

The only reason FOW is considered an auto include in most cEDH decks is that it offers something unique and powerful. There are really only a few situations where it comes in handy but for those situations it is golden.

1)Protect an early wheel or ad naus, which nullifies the card disadvantage.

2) On a combo turn fueled by an ad naus or with the means to win in hand

3) As a last ditch effort to stop someone else from winning.

Outside of Pact of Negation and Mental Misstep (which are more limited in scope) FOW offers something unique and valuable despite its many warts.

As for utility lands, I never play them because I find thier lack of color fixing to screw me often, and thier effects are on average less impactful than a spell. I honestly hate lands and play the minimum I can get away with. The only exceptions are Ancient Tomb, Gemstone Caverns and Gaea's Cradle (in creature heavy builds). The sanitarium is solid though, I must admit.

Holy shit, this is terrifying.

Take my upvote as tribute, oh great one.

Please keep this deck away from me.

Why would you play Trinket Mage over Fabricate? Isn't the second just better? It can get Paradox Engine or Isochron Scepter in addition to Sensei's Divining Top. The 2/2 body shouldn't be important whatsoever. Am I missing something?

I am not playing it over Fabricate, just in addition to. You are correct that fabricate is very nearly strictly better. The only advantage of mage is that I can bounce it with Chain of Vapor on my combo turn. I think mage has enough relevant targets to warrant further testing. I am not commited to the card as of yet.

I am surprised that there's no Anvil of Bogardan in this list, it feels like a staple in my Leovold build (albeit I steal most of my skeletons from you and the other fellas here), is there a particular reason not to run that form of the lock in this deck? Also, Muddle the Mixture seems like it would fit nicely into this as a form of combo protection as well as a handy tutor for any number of things. Any particular reason for its absence I'm missing?

I cut anvil a while back because its good IF Leo is in play, which given his infamous nature is not often. Its very good after a Leo+wheel. Otherwise anvil is a group hug effect and even with leo it is relatively low impact. I have not missed it.

Muddle is a weak counterspell mixed with a limited and overcosted tutor. Its a great budget friendly card, but it does not make the cut in a deck like this which has no budget.

Darkslick Shores?

Can you elaborate in the Primer why this is better than the Paradox Scepter Storm deck that you made originally. Is it just for the backup plan that Leo provides? Other than that, the addition of red for things like Wheel of Fortune or Gamble makes the deck so much better. I guess there also could be color consistency issues.

EnderPlaysCompetitiveMTG: Good call.

Matheyru: This deck is significantly worse than my paradox scepter thrasios build. Thrasios is tailor made for those combos and his access to 4 colors gives that deck an unprecidented level of speed, consistency, and resilience. This deck is an adaption of that brew. While Leo has the advantage of hand locking the table and this version is better than my high tide /DD deck, Leo is still outclassed by Thrasios, which is on par with, if not better than Zur.

Demonic Consultation

markszncd: Demonic consultation is a great combo piece, but I wouldn't want to use it for any other reason in this deck since the risk of exiling all my win conditions or autofolding with it is not worth the potential upside it has in food chain decks. I generally strive to have multiple uses for most of the cards in my deck.

Want to point out that you've convinced me to build this cause I love Leo and the Resovior. Have you considered Heroic Intervention? Seems sweet on a scepter.

EnderPlaysCompetitiveMTG that's awesome man I'm glad to hear it. Intervention has been suggested and its very good. My only issue with it is that it doesn't replace itself and engine is extraordinarily card hungry.

Hello again! How's DDay been? I think it'll always have a place in the deck bc it's just plain strong, cheap, and has a powerful natural synergy with the commander.

One thing i think you'll want to consider shaving, and i know this may be a hard sell, is the dramatic/scepter setup. first, both cards are good but not great on their own, but more problematically, the deck has no particular outlet for infinite mana like Thrasios does. Often with Paradox running I'll find myself with an overabundance of mana and searching for a wincon rather than looking for more things to set up. And its true that scepter+Paradox+some relevant spell usually wins the game, but we have access to a lot simpler combos that utilize pieces which we're either using already (lab man in DDay or Pact lines) or which simply need fewer moving pieces (DD or aetherflux). In other words, while storming off with Paradox i always had something better to do than build a narrow 2-3 card combo from the ground up, and without Paradox, no one piece of the combo is appreciably better than another good cantrip or interaction piece. DDay, Pact/Consult and Aetherflux are more than enough wincons for me!

Individual card questions:

Praetor's grasp: meta pick? seems like a more controlling card than you really want in a combo deck, esp at 3 mana

Kiora's follower/voltaic key: spicy as all get-out, but i'm not sure how crucial these are. when the main plan is to just grab Paradox ASAP, i've never felt the need to run additional untappers. I know there are some s=particular combo lines available her,e but i dont see any of the best ones in this list. Am i missing the sizzling spice?

Whispering madness: a 4 mana wheel? over Day's undoing?? why not just run Personal tutor if you really want more wheel effects? it reduces the CMC and adds another copy of DDay if you need it

pierce: oh man, this is a big step down from Counter-spell just for CMC. I'd be tempted to run the latter and make room elsewhere in the curve.

Overall, i really like the direction of the deck! Leo is evolving rapidly and i strongly suspect Paradox will play a role in his future. Some aspects of all our lists are likely bad old tech lingering from their days as Thrasios and Zur/Jeleva, but i think we're all getting close to extirpating all the skeletons from our closets! Stay in touch and we'll both keep tuning!

JMCraig: Thank you for the fast reply! So far DD has been a nice upgrade. Gush is iffy but occassionally great and doomsday is just a great tutor. The other three cards for the no mana dd pile are incredibly good

Im leaning towards cutting dramatic scepter combo, but dramatic reversal is pretty great on its own. Pretty much a High Tide for us and it helps get us there on main phase ad nauseams like no other card.

Kioras follower and voltaic key are fine untap effects but they also draw our deck with Paradox Engine and Sensei's Divining Top. Given how this leads to our labman win there is no reason for you to not have at least 1 of the 2. Follower has more upside but key is better since it can be assembled on the combo turn to win the game. Ill cut follower since I need more draw/interaction.

Whispering Madness is 4cc but days undoing is worthless on a combo turn. Both have thier warts. The thing I love about madness is its free wheel on a dd turn thing.

Praetor's Grasp is pretty solid imo and is a meta free pick especially when I drop aetherflux reservoir from my list. It can nuke other decks with only one win con but that is not how I use it. Its essentially a grim tutor with upside. Steal someone elses ad naus or wheel. Or just grab another tutor on an engine turn to get doomsday. Or if labman goes bye bye steal someone elses win con.

I dont agree at all with your thoughts on spell pierce. I view it as one of the best counterspells in cedh. It hits almost every key spell in cEDH and can protect our turn 3 Leo+wheel. If mana drain didnt have the ritual stapled to it I would never use that card. Double blue is hard to come by outside a high tide build and its practically unusable on a combo turn. Sure its a hard counter but a soft counter works most of the time.

So if I cut reservoir follower scepter what would you add first?

Have you tried Scroll rack in place of Madness if that's your goal? Its really busted with Ad Naus and/or Engine.

Praetor's sounds spicy as hell, ill have to keep trying there.

You make a good point about counters. I'll have to test that a bit too.

My first adds would be Diabolic Intent, Scroll Rack and Demonic Consultation (literally just for the combo. its that good).

Back from work with a few thoughts:

Dunno if Intent was in there when I commented, but its great. Other potential includes would be Toxic deluge to handle creature decks, and Thirst for Knowledge which i find techy and useful in DDay piles sometimes.

Out of curiosity, why no Necro? its a solid value piece for me, and can obviously dig deep once Im ready. seems like its rarely a bad card.

What's your feeling on Cyclonic Rift? Ive been a little disappointed, honestly. seems like you cut it too. the wheel synergy is fun, but this doesnt seem like the kind of deck that wants to stal and cast a 7-drop.

Have you tried Snapcaster? dunno if you need it with the 2 green regrow effects, but it seems like a solid storm option.

Top+Key+Paradox seems a little Iffy, but i love the idea. gonna try this.

Why Merchant Scroll here? Works great in Tide decks, but it feels litrle subpar here, esp without doing the Scepter/Dramatic thing

and on Skelly's list -

What's Copy Artifact doing? cloning rocks?

Is Sylvan Safekeeper good here? I cant tell!

JMCraig: I did some testing and gush is proving to be fairly problematic with only 7 islands. Is it inconsistent for you at all? I am considering just using frantic search and nights whisper piles and just doing dd after engine is assembled. That makes dd pretty bad outside engine situations though so IDK.

How does scroll rack help with DD?

I added intent after you suggested it. I am playing necro. I like deluge but am not sure I have space given how greedy this deck is.

Rift is very meh. Unless I need a boardwipe I prefer into the roil.

I might try snapcaster since it helps us not fizzle and is good sac fodder.

The key to the top key engine combo is that top.and engine are just plain good. Key is a net positive rock on ad naus turns with our 3cc rocks in play. It also means with engine and one of the two in play a card like fabricate will win the game. Its a combo that can be assembled on the fly.

Merchant scroll replaces itself and like I said before dramatic reversal functions like high tide for us much of the time.

I cut copy.artifact because we need card draw rather than more ramp. I personally dislike sylvan safekeeper but it not without its uses.