So, did Dawn and WOW, this was so different than I expected.
Played Legacy, Tachyon and Tempest, in the Freedom Tower.
Legacy felt fairly similar. Some extra support cards and powers which were nice. Tachyon felt just crazy good, and Tempest was Monstrously good it felt like.
But, part of that was me trying to strategize and waiting to unleash on Dawn after she flipped back. So I had a lot of things I was specifically not playing and not using, because they would have wiped the board and just made life more difficult.
Best play of the game though? I had slightly miscalculated and spent an extra turn with invincible Dawn, but through a lucky draw Legacy had gotten Takedown. So, just as a precaution I played it while Tachyon had an empty deck and Tempest was just nastily set-up.
And yes, you guessed correctly. When Dawn flipped back, the card that I used Takedown to discard was Devastating Aurora. XD
That turn Tachyone unleashed a 30 pt Lightspeed barrage, and by the time the Environment turn came around, Dawn had taken 60 damage and had only 4 hp left… just in time for me to realize that “ally” includes the Tower Guards, meaning Legacy was boosting them +2… and Dawn is taken out by Security.
Immediate Edit before I cleared the game: Legacy boosts Ally characters. Not ally targets. So, he can only boost main heroes, not any other hero targets. Dawn survived with 2 hp 
And played Truth… I still win, but man, that was so close to be hilarious.
///////////////////
I’m feeling arrogant from beating Dawn so easily (Yes, I was playing in the Tower). So, doing Omnitron in Atlantis with…
Fanatic, Argent Adept, and Wraith, since they are the only one’s I haven’t tried yet.
BTW, things that I’ve figured out. I’ve been taking the deck dividers out of the box, and placing the hero hp spinners on those, then, as the hp changes, I rearrange those cards. This makes it very easy for solo play on seeing who is the most hp and least hp, because I just need to look for who is top and bottom on the chart. Then, since I was having troubles distinguishing +1 damage taken from +1 damage dealt, I started putting any modifiers to the hero’s taken damage (armor or breach? I don’t know a good term for anti-armor) next to those dividers instead of in the play area, since all the hp tracking is done over there.
It makes it much easier to parse, IMO.
Updating while I play
Omnitron is mean. Got hit hard round 1, thought Fanatic using End of Days would help… then Atlantis destroyed it before I could use it. This is bad.
Okay, few rounds of getting my teeth kicked in and things are looking like they will end in a victory. However, it all hinged on a specific thing that I might have gotten wrong. Atlantis’s Ritual Room. It says “after any hero does [various elemental damages] put 1 token on this card.” I have Fanatic, and I had Holy Nova. I think this card adds 1 token for each instance of radiant damage, and so I was able to get the 10 tokens I needed very quickly, which led to a bunch of card draw and extra powers, which I turned into a set-up that has let me claw my way from defeat.
But I’ve spent most of the game with 10 hp or less on all heroes (Argent is keeping them alive, along with some timely damage reductions and Fanatic’s self-healing with Righteousness) so I feel like if I was wrong on that card, this victory I feel I am going to get would be false.
Did win. Wraith kept being the best for Argent’s card plays because Fanatic didn’t have much of a hand. So I got multiple cards like leverage and grappling hook played per turn, and eventually had most of my deck in my hand, then Inventory Barrage. Then Leverage and get the items back… Yeah, burnt the robot down FAST once I got out from under his endless parade of devices.