For the discussion of how we, personally, modify the game for balance and just fun.
One rule my group holds to is that Hero effects which "destroy" an Environment card instead do 5 Irreducible damage when used on an Environment target. This is mostly out of mercy to Anubis and Char, who are supposed to be big threats, but just don't seem like it with the number of cards which can effortlessly wish them away.
Consternation over a powered armor character having merely average HP resulted in Bunker being played with 30 HP instead of 28.
We are among those who hold that Absolute Zero is probably the weakest SotM hero, and have had a rotating list of attempts to help with this - using proxies to alter his deck composition, ruling that Glacial Structure gives you card draw whenever it is destroyed (making it a beneficial shield against Ongoing-eating villains like La Capitan or Miss Information), and having Thermodynamics let you discard a card and draw a card in addition to the self-damage are the ones I recall at the moment.
We've deabted playing Tempest's Otherworldly Resiliences as something else, given the oddness one of the most fragile characters having armor for some reason, but never agreed on what.
We've tried a ton of things to make Gloomweaver a threat - who hasn't?
We also increase Advanced Blade's milling by one per turn, to keep it exciting.
Advanced Apostate doesn't get a free Tome Of The Unknowable - he gets a free Profane Summons!
We played a six-player game against Akash'Bhuta where H = 7 and Limbs only do half damage to Bhuta when they die. It was epic but REALLY slow... I don't think anyone wants to try it again.
What have you done?
Ironic