Here's a random, epic battle that simply began with me exiting an area, casting my flame atronach, and preparing to jump on my horse when a dragon goes overhead. My horse wants to help me fight, so I move him to a safe spot. He seems pissed, but stuck. lol I move up a tight valley where I see the dragon attack 4 stormcloak soldiers and 4 Imperial soldiers who were already engaged in battle. My flame atro helps attack the dragon and the soldiers attention turns toward the dragon, as well. Dragon weakens the party with some flying flame action, lands, crunches a soldier in its jaws and proceeds to finish the rest off with some more flame action. As the dragon lifts again, I run into the dead, mis-time my RItual spell and only raise two of the dead. By now, my flame atro is back down the hill after the dragon with me and my 'newly risen' in chase.
Here's where it gets real crazy. Basically, the dragon makes a huge circle around the area I just exited. In the process, it pisses off quite a few things culminating in a full-on free-for-all involving quite the list of characters:
Myself - arrows, fire bolts, chain lightning flying; amongst a couple Shouts for the dragon and my Flame Atronach
Plus,
2 cave bears
1 ice bear
1 witch
1 wild flame atronach (nobody casted it)
1 blood dragon
and
1 innocent mountain goat in the wrong place and the wrong time
(17 total creatures/humanoids fighting in this battle.)
These are just the things I know of. There may've been, and probably were, a couple other things that the dragon may've killed on his way the 'final battle' or things I missed.
The bears and dragon (I do believe one of the bears ran off after incurring mass damage) did most of the damage to everything and each other. The last bear and I helped to finish off the dragon. Afterward, I promptly finished the blood crazed bear and went to absorb a new dragon soul. There can be only one.
For those who don't play Skryim, all of this was completely random, as well. NO scripting.