Evrae Altana can use Stone Gaze, and will use it as its first action. Stone Gaze turns a character to stone and then shatters him/her, putting the character out of action. Armors with Stone Ward are sufficient to give complete protection against it. Interestingly, 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. Evrae Altana will only use Stone Gaze while all three characters are active.
Evrae Altana may counter attacks of any kind with Swipe for 800 or so damage, and its Photon Spray does a similar amount of damage spread out over eight hits. 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. Evrae Altana is also fairly unique among bosses in being vulnerable to Demi and other proportional-damage attacks; this is a trait that was not present in Evrae.