Ike first throws his sword in the air and crouches, preparing to jump. During this time, he gains armor. After the sword hits the apex of its trajectory, he jumps up, catches it, and hurtles toward the ground. Overall, the move is similar in function to Kirby's Final Cutter. The move gives very little horizontal recovery and forces Ike to plummet downward after using it, and as a result, it is often considered to be among the worst recovery moves in all of Smash. However, some argue that the move has decent vertical distance, and the fact that he throws the sword in midair allows him to avoid edge-guarding, allowing the move to be a decent recovery. Additionally, the move's poor horizontal distance is naturally supplemented by Ike's side special move Quick Draw, making Ike's recovery overall passable in spite of Aether's drawbacks.
If the attack is initiated at close range, it hits the opponent upwards and pulls them into a multi-hit combo in midair, which finishes with a spike when Ike swings the sword down and descends, with the final hit negating the spike. As a result, the move can be used as an effective edgeguard if the final hit can be cancelled. If Ike stands on the edge facing away from the platform and performs Aether, then instead of falling off the stage to his death, he will turn around and grab the edge, sending the opponent downwards quickly (often to their death, as few characters have a good enough recovery to make it back to the stage). However, due to being unable to grab the edge until descending, this move can easily be edge-hogged. Although Ike is actively throwing Ragnell during the move, it is not considered a projectile, but rather a disjointed hitbox. Aether is also a good follow-up to his down throw, and its disjointed hitbox can be used to hit enemies through solid platforms, interrupt enemies' aerial attacks, or set off Quark Mines in the Subspace Emissary. It can inflict between 1% and 27% damage.
An interesting note is that if Ike uses Aether six times without landing on a platform (i.e. by grabbing an edge after each Aether), he will not be able to grab an edge on the sixth use, and he will simply fall to his death if there are no platforms beneath him. This is to prevent Ike from stalling on an edge, and is important to know when using any technique involving Aether for Cruel Brawl.
The move returns in Super Smash Bros. 4, functioning similarly to its Brawl incarnation, but without the ability to grab an edge when facing away from it. It also has significantly reduced armor frames, only lasting three frames after the initial throw of the sword.
In Brawl, if Ike is hit while throwing Ragnell in the air and is still on the ground when under the effect of the Timer, he might perform his landing animation for Aether while Ragnell is still in midair, creating 2 Ragnells. He will be stuck like this until Ragnell lands on the ground. Ike will then pick up the Ragnell he held and the duplicate will disappear. Note that sometimes, Ike will simply just stop or Ragnell will instantly land without spinning.
Ike uses Aether in The Subspace Emissary to destroy a Subspace Bomb carried by the Ancient Minister. Interestingly, Ike shouts "Great Aether" as he attacks, although he is clearly not using said Final Smash. This is due to Aether's Japanese name 天空 Tenkū consisting of two parts (two characters; one syllable each) that were split in the sound clip; as this does not work quite as well in English, the name switch was used to fill the line.
Special Move customization was added in Super Smash Bros. 4. These are the variations:
Aether is a powerful skill available to Ike upon promotion in Fire Emblem: Path of Radiance and Radiant Dawn, and later to Chrom and Lucina (or any of Chrom's other female children) in Awakening. When unleashed, the skill deals two strikes to an enemy, combining the effects of the skills Sol and Luna. In Ike's use of the skill, it involves throwing his sword upward, jumping, catching it, and coming down with a spinning cut that heals Ike equal to the damage inflicted (the effect of Sol), followed by a second rising strike that is performed as Ike puts space between himself and his opponent, which halves/ignores the foe's Defense score (the effect of Luna in Path of Radiance and Radiant Dawn respectively). However, neither effect is applied to Aether in Smash, and the second strike is omitted completely.
Aether's custom variation, Aether Wave, references the Ragnell's ability to attack at a longer range. As a magic sword, it has an attack range of 2, compared to the standard melee weapon range of 1, and when attacking an enemy at a range, it release a wave of energy that cuts through the opponent when swung.
The Japanese name of the skill (literally meaning "heaven air/sky") is another word for "the clear sky above the clouds", but it also can translate to ether or firmament; the former of the other two terms is where the English name is derived from, as "ether" with an "a" is another spelling of it.