Ike throws his sword in the air and crouches, preparing to jump. During this time, he gains super armor. After the sword hits the apex of its trajectory, he jumps up, catches it, and hurtles downward.
Aether provides very little horizontal recovery and forces Ike to plummet downward after using it, and as a result, it is often considered one of 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 knocks the opponent upwards and draws them into a multi-hit combo in mid-air, finishing with a spike when Ike swings the sword down and descends, with the landing hit negating the spike. The move can be used as an effective edgeguard if the final hit can be canceled: if Ike stands on the edge facing away from the platform and performs Aether, instead of falling through the stage to his death, he will turn around and grab the ledge, usually gimping the opponent. However, due to being unable to grab the edge until descending, this move can easily be ledgehogged. Although Ike is actively throwing Ragnell during the move, it is not considered a projectile, but rather a disjointed hitbox. Aether is an effective follow-up to his down throw, and its disjointed hitbox can be used to hit enemies through solid platforms, interrupt enemies' aerial attacks, or activate Quark Mines in the Subspace Emissary. It can inflict between 1% and 27% damage.
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.
In Super Smash Bros. 4, Aether functions similarly to its Brawl incarnation but can no longer grab a ledge when facing away from it. It also has significantly reduced armor, now only lasting three frames after Ike throws Ragnell.
In Super Smash Bros. Ultimate, Aether can't clip through the stage, which hinders the safety from recovering with this move. The armor from this move is now significantly increased the armor frames which can help his Out of Shield option. When using a meotor effect, it can KO opponents first which can be useful for last-stock situations. Following the update 8.0.0, the attacking behavior of Aether has been vastly altered from that of its previous incarnations. The landing hit now launches at a lower angle, with significantly increased knockback scaling. These changes render the move capable of reliably KOing middleweights around 115% from center stage and around 70% near the ledge, if all hits connect. Aether's drastically improved KO potential has also granted Ike a new kill confirm from his neutral aerial, albeit only at mid percents when near the ledge.
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 activated, the skill deals two strikes to an enemy, combining the effects of the skills Sol and Luna. When Ike uses Aether in Radiant Dawn, he throws his sword upward, jumps, catches it, then comes 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 treats the foe's Defense as if it was halved or 0 (the effect of Luna in Path of Radiance and Radiant Dawn respectively). However, neither effect is applied to Aether in Smash, and only the Sol portion of Aether is incorporated.
Aether's custom variation, Aether Wave, references the Ragnell's ability to attack at a longer range. It has an attack range of 2, compared to the standard melee weapon range of 1. When attacking an enemy from a distance, it release a wave of energy that cuts through the opponent when swung.
The Japanese name of the skill (literally meaning "heaven air/sky") refers to "the clear sky above the clouds", but it also can translate to ether (also spelled "aether") or firmament.