Great Aether, known in Japan as Great Heavenly Air (大天空, Dai Tenkū) is Ike's Final Smash. It was described by the DOJO!! as a more powerful version of his Aether. Ike becomes invincible and swings his sword in front of him and anybody who he hits is sent upward. He then leaps into the air, slashes the character(s) seven times with his sword aflame, kicks them twice, slashes them four more times, and knocks them downward with a powerful finishing blow, similar to Link's Triforce Slash. Upon impact with the ground, a large explosion knocks away the trapped character(s) and any character that happens to be too close.
 Attack Overview
The attack does about 64%-74% damage (52%-62% from the attack, 12% in the explosion), and is one of the most damaging Final Smashes in the game. If the opponent is very close to Ike when he uses it, the initial hit will deal 15% damage, but if they're further away from him it deals only 5% damage. Because the knockback from the explosion is vertical, opponents may not be KO'd immediately due to the high blast lines on some stages. In most cases, however, the move does provide significant knock back to launch enemies off the screen. Multiple enemies can be picked up in this attack and, although Ike is invincible during this move, Ike's victims can be attacked by other players along the way down. The move elevates Ike to the highest point on the stage and always takes place in the center of the stage. On 75 m and the World 1-2 version of Mushroomy Kingdom, it is an OHKO because the opponent is brought up to the top platform, very close to the stage boundary. On Pirate Ship it can also OHKO, but only on Jigglypuff. The attack can be canceled by attacking at the right time.
At the beginning and middle of the move, Ike yells "Great...AETHER!!" (in the Japanese version, he shouts, "DAI...TEN...KUU!" which can be roughly translated to "Great Aether"). Due to the fact that Ike moves to the center of the stage when this move activates, on some created stages the downswing can be somewhat of a Sacrificial KO. As with a standard Aether, Ike tosses his sword up into the air, and jumps after it, before attacking his foe in mid-air. It can be noted that the site of impact, following Ike's final descent, is determined by the character(s) closest to the ground directly below them.
CPU opponents tend to get hit by this move, even if not caught in the initiation. When they try to "add to the woes" of one caught in the move (as Sakurai suggested at DOJO), they don't understand to get out of the way, when Ike plummets down, and get caught in the explosion.
 Instruction Booklet Description
Take a swing at your opponent and, if the hit lands, finish with a series of powerful attacks. Its success is dependent on landing that first blow.
 Trophy Description
Ike's Final Smash--a powered-up version of his signature move, Aether. Ike faces a foe and swings his sword up for a hit, then tosses his sword into the air, performs multiple nasty strikes, and finally unleashes a mighty overhand blow to send his opponent plummeting down. It's a very impressive sight, but if Ike misses with the first upward swing, he can't use the move.
Oddly enough, this move has never been seen before in the Fire Emblem series. It is possibly a reference to a recurring event in Ike's games known as the "Trial of the Blue Flame", where the goddess of order would be awakened and purge the world of life. However, the flame in Great Aether is regular flame, not blue.
It could alternatively be a reference to the final blow given to Ashera at the end of Fire Emblem: Radiant Dawn, where Ike uses Yune's Power.