The Training Tower is a feature in Fire Emblem Heroes
The Training Tower is a training ground for the player's Heroes. Players can choose from 11 different strata, each comprised of various enemy units. The higher the stratum is, the higher level the units are and the more Stamina is expended to start it. The Tenth Stratum has particularly challenging units who may have unusual skills equipped. Each Stratum also changes anytime a battle is complete, even if it is a Story Mode chapter, Special Map, or an Arena Duel.
Unlike Story Mode, EXP does not scale if the player has completed a stratum before. Completing a Stratum award Crystals upon the first completion of a Stratum daily and will always award Badges. The Badge color given depends on the day of the week.
From the fourth statum and below, the type of enemies you fight in the training tower will always be generic enemies. From the fifth stratum and above, you will fight 4-star variations of characters in the game, with only five-star variations being fought in the tenth (and final) stratum. Also, only characters in the general, summoning poll are fought in the Training Tower. That means no story original characters or characters fought and obtained through Grand Hero Battles or Tempest Trials will appear in this mode. It should also be noted that brave, legendary, or seasonal versions of preexisting characters will not appear in this mode either.