I gotta say, Gilles de Rais (Caster) is one of greatly misunderstood character in FSZ. I know you can't justify his murdering spree in the series but one must understand what droves him to madness to do such dreadful act.
it doesn't excuse it but he was basically driven mad because he couldn't comprehend the church and French Crown betray Jeanne de Arc when they were her biggest backers and the scariest thing is that Jeanne's death was almost exactly the same as what happened to Jesus and in this case Giles was Peter difference is he took the death a lot harder but you should also know that his caster form is how he acted after Jeanne's death he was a child molester and murderer except he did it just to young boys
Giles in this form has mental corruption almost as bad as a beserker because this is him after jeanne de arc(the jeanne he keeps referring to by the way)was burned at the stake and betrayed by the church and French Royalty and he saw Jeanne as the Savior of the world so in a way for him it was like seeing Jesus die himself ...as for Excalibur it's a construct weapon made by the Fae folk that draws strength from the breath of the planet or it's life force so in a sense it's like Goku's Spirit bomb except she's not taking a piece from everything she's literally concentrating all the life force of the planet into her sword
With no problem, he just need to keep shooting the weapons of Gate of Babylon to get to Caster and if somehow that didnt work using EA will destroy it without any problem
