Regarding the West Hills incident in 9:23 Dragon

So, I was reading Anora's entry in World Of Thedas Vol. 2 when I stumbled upon the West Hills incident. If you're unfamiliar with the subject: a farmer said that a hundred giants had taken over his farm near Crestwood, so King Maric sent a scout to verify the claim. After ten days, the scout had still not returned, and both Prince Cailan and Lady Anora had disappeared.
As it turned out, they had embarked on a journey to slay the giants; They later found out that there actually was only one of them. What happened next is unclear, but a woodcutter said that he heard someone shouting about "glory" and "history" (*cough* Cailan *cough*) and, after having climbed a tree to avoid stampeding cattle, that he «saw some kind of spirit, all golden, shouting at the forest and saying, "I command you to go back! I command it!".»
Some time later, Anora and Cailan were found covered in bruises, cuts and ash, refusing to answer to any questions provided by Maric, Arl Wulff of West Hills, or the Royal Guard. Cailan only said that "It's better than the people of Ferelden never know the lenghts to which their prince must go to protect them." and Anora that "We defeated the giant. Now, let's never speak of this again." The giant's burned corpse was later found at the bottom of a cliff almost a mile from the freehold.

Now, it seems obvious that magic was involved at some point in the fight. But how? And why do neither Cailan nor Anora wish to talk about their endeavour? This all seems to suspicious to me. What Cailan said seems to indicate that he had to resort to dealing with demons. But how? He's not a mage. Are they sheltering an apostate? Is Anora an apostate? Lol, my mind is melting.