RNG rates are poor, 1% for a Legendary. They expect you to grind hard for crumbs. You get a Legendary through Rookie Summons. Unlike other games that let you re-roll until you get a result that you like, they set a limit of 5 draws of 10. So if the Legend that you really want is in a draw with 9 other heroe's you don't need or dupes you still have to take all 10 if you want that Legendary. This game relies on elements countering each other. Having a good/decent team of 4 per element is crucial.