Esper Myth

I love the idea going on here. Honestly, my favorite type of build in magic. Control the field and tempo, establish a win condition, resolve the win condition. Its pure, fun, and there are tons of color combos that can do it.

I do see some potential problems in this build, nothing major.

The main problem I see is that there is an imbalance between control cards vs win conditions. lingering souls, luminarch ascension, and myth realized are pure win conditions, meaning they don't really help you gain control until they are firmly established with field position intact. Gearhulk, Gideon, and celestial are combo win conditions that either accelerate or act as control mechanics too. Which means you have 13 win conditions in here (not counting the flashbacked souls), so the math is on you drawing 1 in the opening which should be a dead card that hurts both your development and ability to respond to control mechanics. This is also compounded because you have some good tactical outlet here (opt, spreading seas, azcanta), all of which rotates through cards at a pretty quick rate, cutting down on the slots you actually need to keep available for win conditions.

I'm also seeing the potential for a couple counter swap outs to hit harder and faster on the control end. Remand and Negate should be considered, as remand buys you time and adds tactical control to keep moving through the deck and negate will put a hard stop to everything but creatures (which you have 9 removal outlets to stop). I would consider swapping out spreading seas for remand as its a turn 2 commitment to drop seas and rely on opponent being mana-screwed, whereas remand is reactive and is basically guaranteed to buy you tempo turn 2 and 3.

Fortunately, these two problems fix each other. Drop out a couple win conditions for control elements and you have a quick and sleek control machine.

I suggest losing lingering souls altogether in here. I know it combos wonderfully with supreme verdict, can act as a blocker or a win condition, and gives you 2 waves to tactically get done what you need to get done, but I don't think it fits this build. Souls hits max effect in decks that spam it to the grave like gifts, and you basically don't ever want to drop it turn 3 on games when you're going second, and rarely want to drop it turn 3 when you're on the play as you need to be able to react to opponent having 3 open lands.

I think the gearhulk, 2 colonnades, 4 myth realized, and 2 gideons is more than enough to get the job done in a timely manner. That's 9/60 win conditions with a healthy dose of tactical cards to move through the deck, and 5 of the 9 win conditions double as control elements or acceleration. That's pure synergy right there. Personally, I'm ok with running 3 gearhulks and a couple man lands in a control deck as basically the only win conditions as long as there are good tactical outlets, but that's me. I accept that most people aren't willing to keep it that low. That should give you the room to swap in more counters to keep control until you field your win condition.

Just my thoughts, not trying to tear this build down or anything like that. As I mentioned above, this stuff is my favorite, and I think you are onto something good here. I hadn't considered myth as a potential powerhouse win condition yet.