The boss Ares Savage Spear in Aquila is always casting four times per round, twice before I cast and twice after. This plus his 4500 health and his X cast self in the middle having a fixed amount of damage plus a feint ward no matter how many pips he has in his pip circle equals invincibility. He must be made easier or kicked out and replaced by a gorgon which plays fairly: Medusa Venom Snake. I hope you do something about Ares Savage Spear.
I do believe you're fighting him the wrong way. His cheat is to return each attack you make with an attack of his own. So, understand if you attack him over and over, you're going to lose faster.
Therefore, your strategy needs to be to make a really large hit. If you're a newer player at a lower level, it might look something like this:
add multiple blades to yourself (school blade, triple blade)
heal yourself
add more blades to yourself (pet blade, treasure card blade)
Stop using single target attacks on him and he'll stop getting all the free cheat attacks. He only casts the natural attack every 3-4 rounds for 1 pip, and it's 40% trap, not a feint. As cheating bossing go, he's one of the easiest.
X cast self in the middle having a fixed amount of damage plus a 
gorgon which plays fairly: Medusa Venom Snake. I hope you do something about Ares Savage Spear.
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