Got to the room with the Orb and take a kicking from the imprisoned Draugr. I know he is invincible for ten seconds and the he changes frost/fire/frost/fire as defence.

But I only have an Atronach and fire spells and a shout -- any idea on tactics here? I try to hide but still get waxed.

I was wondering about leaving Tolfdir and my Atronach in the chamber, getting the hell out and closing the entrance door behind me.

A tough fight this, I am level 12 but strat guide says level 6 should be enough.

Does anyone know if Tolfdir joins in eventually when he has finishe with the Orb ?

Tolfdir doesn't usually join in. Just keep using the area as cover. attack him from a position you can hide behind to heal, run, regenerate magika ect...

he was surprisingly resistant to magic but... surprisingly less resistant to a few arrows, do you have a bow?

Yes I do but never used it, I'll try tonight

He'll switch his magic tactics... from frost to fire. While's using fire, he's vulnerable to frost and vice versa. You can use that to your advantage. What can also help is to get up close and hit him as fast as you can while using a shield (if you have one, that is). Sometimes with undead some fast swings with a blade does the trick, as they have no space/time to launch their own attacks.

ok I`ll try that

Tip all Draugr have 50% frost resist so fire spells work much better against them to start.

don't run away... he's only resistant for a few seconds... let your atronoch pull aggro even if you have to dodge around behind pillars and when Tolfdir shouts that he thinks he's got it, kill the draugr.

I did this at level 10 as a conjuration/destruction mage in apprentice destruction robes, hood and leather boots and bracers the first time and it really murdered me. I had to turn the difficulty back a notch and not attempt it on the difficulty I had it set at. I think maybe "difficulty" should be included in the "I did this at [insert low level here] by having [insert skills here]" so the rest of us have some concept of what was really done. I always learn all the spells I can because so many creatures are immune to either frost or fire that having only one of them seems like a handicap.

Good luck. Hope you nailed him. It's a fun chain.