Ethereal Queen is a signature last boss in tri-Ace games.
Keep Jack on the sidelines and do not let him attack.
Every time you see blades of light start to circle EQ immediately start up an Attack Link which will teleport your party to you (to the sidelines) making them completely dodge the attacks and letting you save some valuable items. After the attack link always tell Kain to cure allies otherwise he will attempt to attack, will not heal and you will end up spending lots of items when you shouldn't need to.
Make sure to pack invincibility meds and to use them every 30 seconds or so (to make sure they don't run out and catch you off guard).
Whenever you get 100 volty point tell Elwen to use her volty blast. More than likely hers will do the most damage, (Unless of course you severely out level her/used lots of str items etc.)
Using this strategy it is possible to beat EQ regardless of Jack's level, or the level of the people you are using (as long as they can survive EQs normal attacks) but as long as you pack at least 1 training device its easy to get to the lvl 90+s without realizing it. I will also post of video of beating ethereal queen solo or with an Xchar (Xchar being any character that can survive her normal attacks)
Note: I call the strategy link abuse because it was not meant to be used this way, using the guide below does not consist of link abuse simply because you are using game mechanics that were intentionally added in, not only that but it tells you about using links to share skills in the beginning tutorial.
To do the easiest method to defeating the Ethereal Queen without ever having to level up to level 99 (Although doing so puts players on the safe side), there are certain things players need to do before facing the Ethereal Queen:
- Buy enough herb extract (DX and MAX is preferable) and especially a Celestial Nectar.
- The Guard link.
- Anyone can go with you to face her (However, consider taking Kain and Elwen for the Human side or Gil and Galvados/Gobrey for the Fairy side and of course Valkyrie.)
- Learn all 4 Volty Blasts.
- Learn the command Heaven's Gate Song.
- Get the skill Fierce Defense (Not Zero Defense) and have it maxed out (From Interlude, Edgar, Leona, Wal or Leban]). Now, to win would be obviously easy, even against Ethereal Queen's deadly Armageddon spell. That is if players are quick enough. The key to winning is how you assist your allies, how you fully utilize the Guard Link and use your volty blast to win.
Valkyrie should be able to take care of herself, and so does Elwen and Kain. Battle moderately and keep an eye out for their health. Gil and Valkyrie will help increase the volty gauge. Fully utilize the guard link. With Fierce Defence at max, players are bound to use Volty attacks quickly.
During one of Ethereal Queen's attacks, use the guard link to absorb all her attacks into Volty. Once at max, as the guide above said, use Elwen for the insane damage and also, use Gobrey (Though he doesn't damage too much, he saves more than enough Volty to keep using Guard link)
It also turns out that Armageddon, the most deadly spell of all, is actually the quickest way to end the battle. Be quick to form Guard Link, and you'll see the spell will be nothing more than pretty fireworks as the spell quickly fills the volty gauge. After that, the rest will be easy.