Oh man, all my progress got wiped out. I had over 800 of everything, 500 quadrillion angel investors, every upgrade and manager. Now it's like I had a hard reset done.
I finally figured out the evolution tree. It is pretty cool. I evolved up to Lothan, he was not the hero I started the game with. I went to check my cards after I won the battle, expecting to see Lothan as a usable card. He wasn't there. I think you should be able to use tier 4 units and tier 5 heros in later battles if you've evolved into them in a previous battle.
 "AdVenture Capitalist"){kind=icon}
 "Mystic Cards"){kind=icon}
 "TextRPG: The Rise of Diablo"){kind=icon}
 "Talesworth Arena: Death Watch"){kind=icon}
 "Kaleidoscope Reef"){kind=icon}