Which hero uses their ability first?
Which hero uses their ability first depends on their charge time, their battle power, and their distance to the enemy.
Initial and Regular Charge
Every hero has two charge times. The Initial Charge runs from the start of the battle and sets when the ability first becomes ready. The Regular Charge applies between each use after that.
A hero with a shorter Initial Charge is ready sooner, and one at 0 seconds is ready the moment the battle starts.

Battle PowerWith the same Initial Charge, the
hero with higher Battle Power goes first. Battle Power rises with anything that makes a hero stronger: Levelling up, Ascension, Awakening, Ability level, Barracks level, Equipment, Relics, or Pantheon nodes.
Battle Power is displayed in the hero profile. Tap an enemy hero on the battle preparation screen, or long press your own hero card at the bottom, to open their profile.

Distance to the enemyEach hero also needs an
enemy within a certain distance before their ability can activate. That distance is not the same as the ability's range, which can be much longer. Amina of Zazzau, for example, prioritises enemy heroes even in the rear, but only acts once any enemy unit comes into her melee range.
This distance differs from hero to hero, and some have no requirement at all. That's why a weaker hero, or one with a slightly longer Initial Charge, can still strike first: they act where they stand, while yours has to close the gap.
If your hero keeps losing the opening strike, placing them in a front row usually means they start in range and can use their Initial Charge in full.
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