Faeria

As I didn't find much on the internet written about Jalmyr that really worked (as most of the winning strategies weren't focused on his current deck construction), I feel like that's the best one to focus on as his battle is a savage uphill climb.

We have several problems here:
A)For the first few turns of the game, every time you keep a card in your hand, it goes up by one mana in cost permanently.
B)He's going to hand you an Orb 1st turn, so you'll be drawing another 2 cards, although you will get 2 mana.
C)After a while, he'll add on 1 damage to you each turn for each card in your hand, so you can't just tank a card or two and let it go to 100 mana. (Note, the +1 & damage just seem to go away after turn 15 or so, there's no notice)
D)He plays some brutal creatures and treasures including Doom Scythe, multiple Crystal Dragons, and multiple Lodestone Yaks. So focusing on the one insanely large creature doesn't work as it will just get Doomed.
E)He starts at 50 life. (And the 7 drop lizard that brings a god to 10 is magically made to cost 99 this match.... argh)
F)Any creature that successfully attacks Jalmyr gets taken under his control.
G)If you somehow deal with all of this, he also packs 3 storytellers at the end to deck you into oblivion for the difference he's behind.

Overall, kind of a jerk.

Now, one added quirk is that any mythic cards you happen to be playing will start out one mana less. Most of that is just luck as to the mythics you opened, but parsing through Oversky does reward you with some mythics en masse, and the two that I found to be most relevant were Seed of Paradise and Path to Paradise. Now they cost 1 to make a land, which makes them invaluable in the opening turns.

The decklist I finally made work, we're just going to try and deck him. (Play mythics where you can!!):

1 x Compass of Gagana
3 x Punishment
3 x Queen's Assassin
3 x Safeguard
1 x Laya, Lady of Sculpture
2 x Tower of Curses (honestly, I'm not in love with these, but I did lower a 1/5 into a 0/4 to deathtouch him for free so might not be awful)
1 x Banon, Captain of the Radiance
1 x Wild Growth (because I had one mythic so it was 0)
3 x Faeria Tree (Almost needed in your opener)
3 x Seed of Paradise, mythic earned from Oversky
3 x Path to Paradise, mythic earned from Oversky
3 x Barter (Yup, that's 2 yellow)
3 x Shaytan Assassin (Yup, that's 2 yellow too)

So, your hope is to open with a Faeria Tree and a Seed of paradise. That can give you a turn one of setting up an additional land and getting the Faeria tree pumping. The computer is not hyper-aggressive and has the same locked in hand for the first two turns. The 1/5 guy that gets +1/0 for card draw on the first two turns, and then he also plays a greater wisdom because of course he does. The red mana is only relevant for the path's and are there for fast expansion, so green/yellow/yellow/red is your land choice priority. After that, yellow is preferred so you have more options as to where to dump the Shaytans.

I've come to notice the computer really doesn't 100% know how to deal with deathtouch creatures, hence a compliment of 7 of them in the deck plus the safeguards. Late game seeds can be fed to the Shaytan Assassins for free safeguarding.

The barters will hopefully fetch the computer's doom scythe, as dooming one of his bombs and then running the 6/1 into another is a very high value play. If the computer drew his Doom Scythe on turn 2, well, you're going to have a bad time.

The compass yields near infinite value, and you can get a Thyrian Globe more often than not off the treasure which a 3 drop 5/5 flyer that can zoom across the board and suicides into another 5 damage is valuable. The computer does not appear to believe killing the compass is a high priority, so that's nice.

The other part of the royal flush we're trying to make happen is NOT drawing Banon until the computer has calmed down with the +1's and pings. Playing Banon on an empty deck neutralizes the computer's storyteller path to victory by adding 11 cards to the deck. Unfortunately if this goof shows up in your first ten turns, it's more or less telling you to try again.

So that's how I did it, it's not foolproof by any measure, but it's derpy enough it can grind out the awful end boss and scare up a win through attrition.

And, well, there's 11 other bosses before this, but there's actually decent info out there for them. If I ever get unlazy enough to write a walkthrough, we might tackle those.