Can anyone please tell me how to defeat astral quickly. And why I cannot..

Hmm, First I would answer about that faeries.
First of all about those faeries, you know the faerie town right? Since you are there click one of those houses(If you have, if you don't then make one), then on the house click the one that switches the jobs, click "Troops", now that that's done you put a faerie or three faeries there, now you can use faerie attacks, note also that there is also a amount of the faeries to initiate a vertain type of attack, for example, the faerie charge requires a full 20 faeries, to do that use all of your faeries and put it all under the "Troop" houses, note also the level of faeries increases when you use it.

Well... To defeat Astral.. I only beated it on level 32, here are the techniques I have done, but I dunno if this can apply to you. I used all the upgrades and putted it on Ryu, then after that I casted Celerity on Ryu, after the second turn, you should cast Vitalize/Vigor on your allies, if they die use Benediction, put it on anyone that can live, and put Cray on the front, and let him use Shield, oh and... Save the Ambrosia if all your dragons die, and after that you should be fine. By the way, before that you should buy wisdom seeds(buy at least 50 that give 30 AP a single person, you can buy it on the faerie town, any kind of faerie will do, and be sure you are under Khan, because if you die, you will live again, course it is much better if you buy manly clothes and soul gems(more easy to find at stores), and the manly clothes from a diligent faerie on the town.