Aither

Low Cooldowns

Aither's S2 has a 2-turn cooldown, and his S3 has a 3-turn cooldown. With such a quick turnaround, it is easy for him to spam both skills to keep his allies healthy.

Lots of Utility

Every one of Aither's attacks has some form of utility attached to it. His S1 adds a Speed Break debuff, which helps him keep pressure on Wyvern when he needs to attack. His S2 is a single-target heal, but it also cleanses two debuffs from an ally and increases Aither's CR, getting him to his next turn more quickly. His S3 is an AOE heal that also gives the team a Barrier. That's a lot of utility to cram into one moveset!

Free to Pull

Since Aither is a free unit who is given to the player shortly after they start the game, you don't have to worry about whether or not RNG will pull him in the Covenant Summon for you. Being a guaranteed hero is a massive blessing in a game with as much unpredictability as Epic Seven.

3★ Hero

Being a 3★ hero has multiple advantages in Epic Seven. For one thing, it makes Skill Enhancing Aither a lot easier, since he uses the common Stigma resource instead of the rare Molagora resource to upgrade his skills. For another thing, being a 3★, most players should be able to pull additional copies of him from the Covenant Summon, making it easier to to promote him and upgrade his Devotion Aura.

Terrible Stats

Aither has very high natural Def, but he is close to dead last in every single stat other than Def. In particular, his atrocious Spd is a real blow -- his low-cooldown skills are meant to be spammed, but his turn speed is so sluggish that he may not always be able to act when you need him.

Needs Atk to Heal

Aither's healing skills scale off his Atk stat. This might sound like a good thing at first, since it sounds like he can have high damage and high healing output at the same time, but Aither's damage is going to be terrible even with high Atk. It would be much preferable to build him with HP and Def so he can survive longer, or with Spd so he can take more turns and heal more frequently. Instead, he is forced to build Atk to maximize his healing, which is easily his least useful stat.

Can Fall Behind as a Healer

Between his terrible Speed and his heals scaling with Attack, it is very easy for Aither to become overwhelmed and be unable to keep up with your healing needs. When well-geared, Skill Enhanced, and/or assisted by an off-healer like Lots or Elson, Aither can hold his own, but once you can Specialty Change a better healer like Montmorancy or Hazel, Aither is likely to fall off your radar.