well... the ghosts might've come from nearby ruins but they coensided with a thu'um it used that didn't do anything else. the dragon was named, so he probably respawns if you don't kill him persionally, deprive you of the fight and all that.
the foresworn were raised as zombies, one at a time, it was night so there could've been a vampire or one of their hagraven nearby but I still blame the dragon.
on the offchance, can hagravens raise dead? I don't think they can, don't know all of what briarhearts can do either, each one has cold powers, but I've seen varied spells. usually I take them out as fast as possable.