Nessie, the Lochness monster (EDH / Commander)

The main strategy of the deck relies on aggressive ramp and additional draws provided by the commander. There are several win conditions and combos that can be assembled differently in order to win the game.

The deck is strongly centered on the commander, a strong draw and ramp engine. Therefore, in the first turns it is important to cast it as soon as possible and protect it by opponent's treats. Aesi, Tyrant of Gyre Strait provides you a significant card advantage, especially if you combine its triggered ability with cards such as Trade Routes.

The main win condition combo aims to draw entire deck playing an infinite number of lands and triggering infinite times the ability of Aesi, Tyrant of Gyre Strait. The fundamental piece is Retreat to Coralhelm. In details:

1) Aesi, Tyrant of Gyre Strait + Oboro, Palace in the Clouds + Retreat to Coralhelm + "scout" creature (Llanowar Scout, Scaled Herbalist, etc): play Oboro, Palace in the Clouds by activating the ability of "scout" creature, untap the latter with the trigger of Retreat to Coralhelm, and draw a card because of trigger ability of Aesi, Tyrant of Gyre Strait. Tap Oboro, Palace in the Clouds in order to bounce it in hand. Repeat the process.

2) Aesi, Tyrant of Gyre Strait + Oboro Breezecaller + Retreat to Coralhelm + "scout" creature (Llanowar Scout, Scaled Herbalist, etc): combo similar to 1). Here, you bounce the land activating the ability of Oboro Breezecaller: tap two lands for the ability, one of them bounces in your hand and the other untaps.

3) Aesi, Tyrant of Gyre Strait + Simic Growth Chamber + Retreat to Coralhelm + "scout" creature (Llanowar Scout, Scaled Herbalist, etc): same combo as the aforementioned ones (1 and 2). In order to bounce the land, you can use Simic Growth Chamber and bounce itself.

Worthy additions: Lotus Cobra or Nissa, Resurgent Animist. In this combos you can exploit it to have an additional one mana every time you repeat the loop.

In absence of Retreat to Coralhelm you can produce infinite mana and draw the entire deck as following:

4) Aesi, Tyrant of Gyre Strait + Summer Bloom + Mystic Sanctuary + Oboro Breezecaller + Simic Growth Chamber: play Summer Bloom and up to three additional lands, chose to play Mystic Sanctuary (first land), put on the stack its ability in order to draw the card that you would draw with trigger ability of Aesi, Tyrant of Gyre Strait. You have Summer Bloom in your hand again. Tap Mystic Sanctuary for mana and bounce it playing Simic Growth Chamber (second land). Play Mystic Sanctuary (third land), tap it and activate the ability of Oboro Breezecaller: bounce Mystic Sanctuary and untap Simic Growth Chamber. Repeat the process again re-casting Summer Bloom with the mana produced by Simic Growth Chamber and drawing entire deck with trigger ability of Aesi, Tyrant of Gyre Strait.

5) Aesi, Tyrant of Gyre Strait + Ghostly Flicker + Mystic Sanctuary + Lotus Cobra / Nissa, Resurgent Animist + land: play Ghostly Flicker and target Mystic Sanctuary and another land used to cast Ghostly Flicker. On the stack you have trigger ability of Aesi, Tyrant of Gyre Strait and Mystic Sanctuary. Order them so as you put on the top of the deck Ghostly Flicker and draw it with your commander. Meanwhile, with Lotus Cobra (or Nissa, Resurgent Animist) you can produce two manas. Use these manas to re-cast Ghostly Flicker and tapping Mystic Sanctuary. With the first target the second and a land. Repeat the process until you draw entire deck.

6) Aesi, Tyrant of Gyre Strait + Ashaya, Soul of the Wild + Quirion Ranger: with Aesi, Tyrant of Gyre Strait and Ashaya, Soul of the Wild on the battlefield, cast Quirion Ranger and draw a card with your commander. Tap Ashaya, Soul of the Wild to produce one green mana and activate Quirion Ranger: blink the latter and untap the first. With the green mana in pool, re-cast Quirion Ranger and repeat the process in order to draw entire deck.

After assembling the infinite mana combo and drawing entire deck, you have four win conditions at least.

WINCON 1
You can cast Reality Shift on opponents' creatures and manifest their first deck card. Retake Reality Shift from graveyard to your hand exploiting the trick of Aesi, Tyrant of Gyre Strait and Mystic Sanctuary. Cast Reality Shift and target the manifested tokens. Repeat the process until you mill each opponent deck and win the game. In case that your opponents do not have creatures on the board, you can start this loop casting before Beast Within and targeting the beast token with Reality Shift.

WINCON 2
It is identical to WINCON 1, but here you can exploit this alternative trick to retake and recast Reality Shift. With Ghostly Flicker you target Eternal Witness and Mystic Sanctuary. On the stack of Eternal Witness, Mystical Sanctuary and Aesi, Tyrant of Gyre Strait, you combine the triggers in order to retake Ghostly Flicker from graveyard to hand, put Reality Shift on the top of your deck and draw it (or vice versa).

WINCON 3
If you draw entire deck, you will also draw Thassa's Oracle and Jace, Wielder of Mysteries. Cast one of them and win the game.

WINCON 4
If you have Walk the Aeons + Ramunap Excavator / Crucible of Worlds + Azusa, Lost but Seeking / Dryad of the Ilysian Grove + Aesi, Tyrant of Gyre Strait, you can play infinite turns and win the game either with commander damages or finding an aforementioned combo. Here, the most important things to bear in mind are: you must be able to play three lands (including the land of turn) per turn at least; and you must have the possibility to play lands from the graveyard.