When I first got Belias, he pwned. When I got Mateus, well I got Adremelech shortly afterwards so he didn't look too good in comparison... Adremelech, wow, he was floating around killin stuff like Freeza or soemthing O.o
I just got Cuchulain, could be a little more helpful but, his one hit pwntage is... well, pwntage. I love espers so far! And they do come very useful in boss battles, I beat the 2nd judge without doing anything, Adremelech did it all for me.
I love Espers as much as Quickenings. <3