Elsha of the Infinite Top Combo (EDH / Commander)

Summary
The object of the game is to have Elsha of the Infinite in play along with Sensei’s Divining Top and one of our cost reducers. From this state we can draw the library and assemble any of our wins, limited only by opponents' boardstate and exaclty which of our pieces have been removed or exiled. In general we want to draw the library, generate enough (or infinite) mana, and loop our spells to win. This deck currently plays at a high but sub-competitive powerlevel, but can interact on time and hold its own at a competitive table with a little luck. We make up for our lack of fast mana by playing at a slightly midrange-esque tempo and trying to stick value engines if allowed to.

Generating infinite mana
In ideal circumstances, with library in hand, the first step is to cast Silence to turn off our opponents answers later on. The second step is to cast any 1-drop artifacts we have and play the second of our cost reducers. Now our 2-drop artifacts are free and we can play any that we haven't already. From here we need 5WUUUU, which we either have from our lands and rocks or need to make up.

In general, if we don't have what we need, the easiest way to make up the difference is by looping Dockside Extortionist. We have 3 spells which put it back into our hand for just U (Chain of Vapor, Winds of Rebuke, Snap), one of which refunds 2 mana of any colour we like, and three spells which kill it (Rapid Hybridization, Deafening Clarion, Lightning Bolt), allowing us to return it with either Sevinne's Reclamation or Underworld Breach, depending on how many other cards are in our graveyard and how many artifacts and enchantments the opponents have. In the worst (successful) scenario, where we have only R and a card in our graveyard (Lotus Petal fulfills both these requirements), our opponents need only 3 combined enchantments and artifacts for us to secure the win with the following example sequence.

1. For R we cast Dockside, generating 3 Treasures.
2. Spend 2 treasures to cast Chain of Vapor and recast dockside, total 4 treasures.
3. Spend 2 treasures to cast Winds of Rebuke and recast dockside, total 5 treasures.
4. Spend 2 treasures to cast Snap and recast dockside, total 6 treasures and 2 untapped lands.
5. Spend 3 treasures to cast Underworld Breach, Snap (exiling Chain, Winds, and another card in the worst case, and three lands in the best case), total 6 treasures and 4 untapped lands; i.e., 10 mana.

With our 10 mana in any relevant combination of colours, we can cast Smothering Tithe (2W), Echo of Eons (3UU), and Narset's Reversal (UU, targeting Echo). Each player shuffles up and draws a new grip of 7, requiring 14 mana from each of them lest we end up with the resources to continue on. We draw our library once again with Top and loop as many times as desired. It's important to mention that without Narset's Reversal Echo of Eons ends up in the graveyard, leaving us with limited options.

Winning Loops
With infinite mana and library in hand, we have many winning lines. I will list the three I most commonly use:

Cascadia: While we were making infinite mana, Elsha has been on board getting larger and larger due to prowess triggers. At some point her power will have become greater than the life total of each of our opponents. We can exile her with Swords to Plowshares to gain at least that much life and cast Earthquake for the same value, reducing each of our opponents life totals to 0, causing them to lose the game.

Out of Mind: Drawing our library after having cast Echo of Eons will usually give us upwards of 80 cards in hand and an empty library. We can cast Angel's Grace and Underworld Breach, if we haven't already this turn, and follow up with Windfall, dumping our hand and causing each of our opponents to draw the majority of their cards. We can then cast Windfall a second time to clear out our opponents' libraries and causing them to lose the game.

This win is also available to us without first generating infinite mana, as long as at least one opponent has 6 or more cards in hand and we have Underworld Breach, Windfall, and Lion's Eye Diamond. Simply activate Diamond to cast windfall and exile the cards we've just dumped into the graveyard to pay for the next iteration of the loop.

Bolt from the Blue: The way our win has been set up allows us to cast a single spell an arbitrary number of times by casting it in between Echo of Eons/Narset's Reversal casts. For example, we can cast Lightning Bolt on our least favourite opponent, Echo/Reversal, draw thelibrary, and repeat, slowly bolting each of our opponents until they lose the game.

Notable inclusions
Cards whose inclusion I feel should be commented on:

Future Sight represents a redundant combo piece in case the commander gets too expensive to cast in a drawn out game. It is also an amazing value piece, allowing us to effectively draw many cards per turn, including lands, and do so through a Spirit of the Labyrinth effect. While UUU is sometimes painful, subsequent turns can more than make up for it, especially when you can make land drops from your top deck; a turn 2 or 3 Future Sight is not to be underestimated and well worth the loss of information. Showing a counterspell on top can sometimes bully opponents into allowing your spells to resolve uncontested when they don't have a follow up or prevent them from trying to play their own win conditions.

Scroll Rack is a way to get the combo off the ground at instant speed if we have the right pieces in hand, since if Elsha is in play we can put the relevant pieces on top of our library and play them in response to some other threat or counterspell war. If we have a cost reducer in play, which we should if we’re drawing everything, all our rocks are mana neutral or positive. This line became much less possible with the removal of dramatic scepter combo since we no longer have a way to untap rack any time we like, but we keep it around to protect ourselves from wheels and grind value off fetches and tutors.

Narset's Reversal is one of the more versatile pieces of interaction in the deck, ensuring our winning loops and protecting our instants and sorceries, but has the potential to make huge tempo plays in the early game by stealing the green player's Rampant Growth or Farseek, or the black player's Demonic Tutor. Especially when used early, there isn't much the opponent can do and they end up either losing a turn while we get the early play they kept their hand around or pitching a Force of Will or similar for their modest value piece. It also feels incredible to steal an Ad Nauseam, but players usually avoid such attempts into open UU.

Underworld Breach is a huge include for the deck, allowing us to get back any spell in the graveyard for a marginal cost. In a pinch this lets us dig topless, so to speak, by casting Windfall repeatedly to get to the pieces we need. Breach can also function as a value play, getting us back a tutor or draw spell, or even ramp us back after a Bane of Progress or Vandalblast. The addition of Lion's Eye Diamond is a big powerup for Breach.

Sevinne's Reclamation gets us back top and can recur an Underworld Breach, but can also function more modestly as a ramp spell, recurring one or more of our lands or Dockside Extortionist. Recurring Breach for value can get addictive, so take care not to put yourself down a recursion spell prematurely.

Cursed Totem works well in my meta of creature activation value engines and wincons, but may be better swapped for a torpor orb or similar depending on what you expect to see across the table. This shares a slot with Verity Circle and in a dork-heavy meta, I prefer the enchantment.

Overburden is a spicy meta tech. Because of our lack of creatures, it doesn’t really hurt us, and if we would miss a land drop we can make up for it by playing a creature into it. Opponents often have many more creatures than we do and its effectiveness against these decks is often worth the price of either being situationally dead (eg. against Chulaine) or holding us back. It can also allow us to buy back Mystic Sanctuary, which with Elsha in play can sometimes unexpectedly accelerate us to a win.

Lion's Eye Diamond allows us, for the small price of discarding our hand, to generate a free three mana. Used in response to our own cantrip or other draw spell, we can set ourselves up for an explosive turn. Meanwhile, its synergy with Underworld Breach allows us more avenues for victory. This is not a mana rock on which to rely for early game advantage, but can be a great tool in the middle to late game.

Closing Words

I should mention that this list is entirely cards I own, so there might be some glaring omissions especially for making the deck competitive. Cards I would add if money were no object include (in no particular order) Chrome Mox, Mox Opal, Mox Diamond, Mana Crypt, Timetwister, each fetch land minus Verdant Catacomb, the three ABUR duals, Mana Drain, Gilded Drake, Wheel of Fortune, Force of Negation, Ancient Tomb, Tabernacle at Pendrell Vale, Fierce Guardianship, Deflecting Swat, and Lore Drakkis.

Maybe board:
Verity Circle
Containment Priest
Stifle
Counterspell

I am indebted to Flash_Andretti for his list (http://tappedout.net/mtg-decks/cedh-primer-to-infinity-beyond-1/), whose earlier versions this deck is largely based on and the Elsha of the Infinite cEDH Discord for helpful discussion.