If you are having difficulty clearing the final stages: Beginner’s Strategy Guide to Challenge events
If you are looking for Strategies to Maximize your scores
Majority of Monsters: Fire
Therefore you will want to bring ICE heroes.
*Multiples of a single hero can be used.
**Heroes are planned for mono color usage – to maximize the chance to be able to clear the first wave of enemies with a good cascade of tiles. Alternative hero choices here
2019 December update: Miki should be used for attack modifier hero for Legendary Challenge