Is going to the Labyrinthian a smart idea at level 19 almost verging 20?
I ask this becuase originally my mage character, the first one Rothion was lvl 5 when doing the Mzfutl quest Revealing the Unseen I believe and was getting his major toosh wooped. But then I restarted a mage character and made Helios who is total bad ass at 18 he did what Rothion cuouldn't in Mzuftl [or however you spell it].
I did it at around 23 IIRC dont think 3 levels will matter that much.
It should be alright if you have a decent skill up in destruction and can spam spells for long enough, some fights will be hard and long, but overall not many threats in there.
I heartly advise you to take health increasing potions aswell as shock resist potions, not going to say why not to spoil stuff, but it will be pretty clear when you will need them.
ps: master difficulty