tel me what lvl can idefeat gyendal

Gyendal is so tough, I can't beat up his ass.
and Stella join his party either.
tell me what lvl can i defeat gyendal.
i am only LEVEL 79.

battle with mel,edward,lydia,galahad....
lydia must use siren all through the battle
mel must use trip on stella
galahad and edward must use physical attacks

it doenst work at all...
I finally defeated Gyendal by using physical attacks, I dont worry about stella for healing gyendal...
coz i used him a plague scroll....
If gyendal uses cures or lightning,
I use a Elixir to heal and purify....
by the way.. tnx for the tip...

where can i find the plague scroll?