I'm on Bitterblack Isle & after meeting Barroch in the courtyard & exploring some, I climbed over some rocks to reach a courtyard that has stairs and a door. The entrance leads to the stairs going down and then a circular stairway to a hall or something. Here, I meet a dragon or so that emits fire and has its heart exposed on its chest. I don't know how to kill it. When I shoot at its heart or head with the arrows it eventually falls down but then it doesn't seem to get damaged. I go near it & strike at its heart but it kills my pawns & me almost instantly. I'm safer shooting arrows at it from top but it doesn't seem to do much other than bring it down to the ground for a little while when my pawns shout, "It's heart lies exposed." I've tried but I can't find any guide to this boss. I'm not even sure what its called in the game. Can anyone please help?
Edit: From this Gamefaqs
link, I think it's a FireDrake that can be damaged only with Ice.