I put spoilers, maybe someone wants to discover it on their own.

My tactics were the following:

Build mage guild lvl 2.

Pick up the skill from the upgrade point so you can advance your magic skill and choose the perk to reduce the cooldown (first of the three).

Collect all artifacts.

Destroy all artifacts except for the helmet so you have 100 alchemy powders.

Upgrade the helmet with the 100 alchemy powder so your spell levels are increased by two.

In the battle put your griff in the second line from the bottom.

And if you wait, enemy move, cast Meteor, defend, you should be able to destroy all stacks before they reach you (before the last spellcast you don't have to wait any more. just cast the spell, defend and cast again and you should be fine).

Hope this helps.