If I remember correctly, no. You can get into the castle either by teleport (along the Rennie quest chain), or by killing the giant, go to the right of the gate along the wall, there will be a staircase near the cemetery.
MrRedGrave This is true if you're going through Ranny's questline and there's a festival in the castle right now. After killing Radan, closed doors will open in the castle and opponents will appear.
