The Witcher 2 - How to defeat the Kayran boss fight

I found the best plan is to go off to one side of the creature and then use the Yrden sign to trap it's tenticles then hack them off. You may also want to use the Quen sign to give yourself that extra buffer of damage absorption, but it will usually collapse after one hit from the Kayran so I personally don't think its worth it. Might take you a few tries to get the timing down.