This has been discussed in great length:
http://www.thenexusf...-attack-helgen/
To sum it up, somewhere in between:
* After coming out of the time whirl just been mad and attacked the next townat the throat of the world (its pretty close to helgen)
* After coming out of the time whirl confused and realized only after the attack he is in a completely different timezone.
* He senses the dovakin (He says "(dragon bla bla) dovakin" somewhere at helgen!) and is just nosy what you are capable of.
* He plays with you like a cat that plays with a mouse before it eats it, just you escape.
* After the encounter he considers you puny and not worth his further attention.
* Its his idea of a welcome party (his welcome back to the world, or your welcoming).
To explain it out-of-universe: of course, just Beth wanted to start the game with a bang and never bothered to come with an explanation ex-post.
He is certainly not:
* There to kill you - otherwise he would just await you again you when you exit the dungeon, to finish his job. He also shouts unrelenting force upon you when you are at the block, a firebreath instead would have finished you off. (He tests how you react)
* There to rescue you - he kills you without any sorry if you are in his way. Nor does he ever help you again, thats why I refute these "mystic binding and helping arguments"
* There to rescue Ulfric Stormcloak - he has no idea who that guy is, since he doesn't dialogue with human affairs.
Edited by faifh, 17 January 2012 - 11:23 PM.