Map of Castle Ansilla
1 - Private Gautliffe
2 - Exit
3 - Doll Asnilly
4 - Lever
5 - Ticneri
6 - Til's Collection
7 - Soulbind cure
8 - Conni
As it turns out, there is only one alive - Ridge Gautliffer. You'll find him in the third large chamber.
Help him in the fight and then talk to him. He will tell you that Tuatha's leader is the man named Ticneri.
Run after the man until you reach the lever, which unlocks a passage to the chamber with enemy.
Once you get inside, a large Tuatha squad will attack you. Kill weaker enemies with area abilities and then attack Ticneri.
The priest is not a tough opponent, but just before his death he will put a curse on you, which decreases your mana by 50%.
To get rid of the curse you have to get the cure from the eastern wing of ruins.
Take it out of the chest and drink it.
Once you are healthy again, return to the general to end the mission. He awaits you in Odi's Camp M11(2).