Evrae Altana opens with Stone Gaze, turning a character to stone and immediately shattering them, removing the character from battle. Evrae Altana's Stone Gaze also has a 50% chance of inflicting Sleep; however, as it inflicts it for zero turns, it has no impact. If a party member is petrified, Evrae Altana will only use Photon Spray afterwards. Otherwise, it will alternate between the two abilities. It will also counter attacks of any kind with a physical attack for 800 or so damage, while its Photon Spray does a similar amount of damage spread out over eight hits.
The party can choose to fight Evrae Altana, or use Trigger Commands to break the locks on nearby underwater gates to escape. The battle takes place over three areas, and moving to a new area will revive any fallen or shattered party members. If the gates are opened twice, Evrae Altana will no longer be able to counterattack.
Going through the gates is not recommended, as it isolates the party from the next save sphere and item chests containing the Avenger and Rematch counterattack weapons. The fastest and easiest way to beat Evrae Altana is by using two Phoenix Downs or two X-Potions on it, while armor with Stone Ward is enough to protect against Stone Gaze. Evrae Altana is also fairly unique among bosses in being vulnerable to Demi and other fractional damage attacks; this is a trait that was not present in Evrae.
If the player wishes to have all three of their characters gain AP from this battle, they will need to have all three get a turn. It is possible that Wakka (the slowest of the three) will not get a turn before Evrae Altana does, and thus not get a turn at all if using the Phoenix Down/X-Potion strategy to kill the boss as soon as possible. Giving Wakka a weapon with First Strike, or having Tidus cast Haste on him, may help. Alternatively, giving all three characters armor with Stone Ward allows Wakka to safely act after Evrae Altana's initial Stone Gaze.