In FF4's ATB system, speed in battle is primarily determined by a stat called Relative Agility (RA). This value is used when setting the Action Timer, which determines how many ticks must pass before a character or monster can act. For more details, see the articles on Battle Timers, the ATB system, and Battle Speed.

At the start of battle, all participants (characters and monsters) are assigned an RA value based on their Agility stat compared to the anchor's Agility stat, according to this formula:

RA for Slot X = (Anchor's Agility * 5) / (Slot X's Agility)

The result is rounded down. If the result is below 1, it is set to RA1.

If either agility value in this equation is zero, the result is RA1.

• This means that if the anchor's agility is exactly zero, all participants in the battle will be RA1.
• This also means that if a character has zero agility, they will be RA1 regardless of the anchor's agility.

RA does not change in battle.¹⁾ However, the Speed Modifier, which is altered by spells like Slow and Fast, gets applied to RA to determine the actual value that the Action Timer will be set to.

If the -vanilla:agility flag is enabled:

• If Cecil is in the party, the anchor is Cecil.
  • If multiple Cecils are in the party, the anchor is the Cecil in the highest priority slot.
• If Cecil is not in the party, the anchor is the character in the highest priority slot.

If the Chero flag is enabled:

• If the -vanilla:agility flag is enabled, the above rules apply.
• Otherwise, the anchor is the hero.

If neither of these flags is set, the anchor is the character in the highest priority slot.