“Elia’s Quest” – “The Showdown” [Campaign 3, Mission 5]

I don't understand why everyone finds it so easy. My Ilaya and Isabelle barely manage to reach the top, and then a demon chases after them (it even kicks up dust). And at the top, I don't really have a choice – either fight off the demon or attack the red creature that's attacking Duncan. I tried not to engage the demon, but it just heads towards the castle and devours Duncan. And if I kill the demon, I don't have enough strength left to deal with the red creature... In short, I've tried five times, and every time the scenario unfolds the same way – I get hit at the very beginning, and that's it...