Welcome to the Fallen Angel Hero Guide. Fallen Angel is the only hero that asks you explicitly to combine good and evil.
Fallen Angel's Hero Power is all about the early and mid game. +2/+2 to your team is more than almost any other hero power can give at that point in the game.
With Fallen Angel, your goal is to trigger one side of her ability as early as turn two or three. From there, you should dominate for a while, and then transition into a strong late game comp.
Your first goal is to meet one of Fallen Angel's two conditions. Try to have either three Evil characters or three Good characters starting on turn three. From there, simply meet the other condition. Your secondary focus should be on characters that are good with stat buffs. That includes Ranged characters like Shadow Assassin, and token makers like Princess Peep.
As you transition to the late game, you have a few different options. One is to play something like Bearstein Animals that both uses the buffs well and can continue to play a mix of Good and Evil characters. Another is to play something like a Pumpkin comp that retains just the Evil buff and likes it. The third is to simply ignore the Hero Power completely and simply play a strong late game comp like Treants. This can be especially effective if you use your midgame advantage to buy XP.
Skip's Puzzle Rune, Locked Chest, Treasure Map. Take advantage of your early and mid game strength to go for greedier treasures.
These are real player comps, courtesy of Untapped.gg's Storybook Brawl site!
Tips and Tricks / Key Combos
Time Flies will get the Fallen Angel buff even if it starts in your hand.
It's totally fine to use only one side of the Hero Power later on. Giving your characters +0/+2 with a Good Boy comp, or giving your characters +2/+0 with a Pumpkin comp are both solid.
While simple in theory, the trick with Fallen Angel is figuring out how to get from a comp that can dominate the mid game to one that can dominate the late game. If you can make that transition well, Fallen Angel will likely be one of your best performing heroes.