Riovannes Castle? (sp?) Yeah, it's pretty tough. Good luck! It does make for a fairly epic end to chapter 3 though.
I just finished chapter 3. Belias was pretty tough even at level 70. He ended the fight with Stone 3 times in a row so I had to Tailwind to 50 and Focus to about 35 during the Weigraf fight. Then I was able to kill him before he got a chance to attack. It took some time but it's done.