Taking the Monastery
As the game suggests, it's a good idea to drink a Cat p otion now. Go ahead and mediate, then drink it. It's also not a bad idea to take a Swallow potion too. There will be a lot of fighting ahead. Move forward and switch to the silver sword. There are some drowners down here, and the steel sword won't work well against them.
For the most part they just come one at a time. Just use the usual hit and run tactics to smack them around and kill them. The passage isn't that interesting. There are some side alcoves with weak walls that can be knocked down with Aard signs, and you'll need to do this to clear the path. Other than that though, just follow the map out to the ladder. Go ahead and go back to your steel sword too. There are only humans ahead.
Move up and note the S'coiatel on the shore. There's nothing we can do about them now though. Just keep moving up and around until you wind up with a few soldiers. You should have no trouble with them. Keep going until you get to the blocked off entrance to the main room. You'll need to climb over the wall and go around on the outside path through the cemetary. This will take you up to the main entrance.
There are a few door guards, so just take care of them as you did before, then open any of the doors and proceed to the main courtyard for the big brawl.
This is the time to really look in your inventory. If you've been following my guide, then you haven't dipped into your trap stashes. Move a few of the bombs into your pockets. You should have five of the shocking bombs, which will make the battle a whole lot easier.
Move through the gatehouse (you need a key to unlock the gate, and we'll get that in a second) and then walk into the courtyard. It's time to start fighting. There are a few options for this one. The Axii symbol will actually work well here. If you hold it for a few seconds, you can brainwash someone into fighting for you for a time. That will do wonders for splitting up the groups. Aard is good for nocking back the heavy knights, and Quen will make you survive much better.
The key is to start thinning the field though. Use a few bombs when the cluster appraoches. the damage isn't bad and the stunning effect is great. Leap around and start picking off the weak men. Once they're dead, you can start using Aard to stagger shield users and then take them out with a quick slash/strong hit combo. Once it's down to the knights, just parry their hit and then hit them while they're stunned. Make sure that you loot the remains though. The biggest guy is the gate guard, and he has the key to the gatehouse. Grab this, go back inside and then use it on the locked cage to let you open the gate.
Walk back out to meet back up with Foltest and his guards, and continue the game.