I mainly used three spells there, besides the standard shield and healing spells:
A water AOE: QQQQQ shift-right click, to throw the enemies back and stun them
A very powerful lightning beam boosted with steam, twice: QFQFASA right click (same key combo as thunderstorm) (I was using QFAS at first, and then switched to QFASA when I learned thunderbolt, and then added the extra steam when I noticed it doing damage faster.
(It looks like having three steam instead makes it deal damage even faster (QFQFQFAS), for some reason. I usually don't bother since the two-steam version is already ridiculously powerful.)
An electric exploding icewall: QERRAS shift right click, or shift left click to put on the sword and then use the sword again to throw the icewall in a straight line. You can cast this (with shift right click) whenever enemies are starting to get close to blast them, and then recast it while the icewall is exploding to whack them again when they start coming at your again (or even before). I discovered this one while experimenting with five-element spell combinations to see which ones were most useful.
Those last two/three are on the
Magickapedia's spell combinations list, it turns out, although they have the keypresses in a different order (it shouldn't matter, elements appear to be commutative except for casting Magicka), as the most damaging spell combinations known currently. Magickapedia refers to them as: Super Steam Lightning Beam, and the version with three steam as Ultra Steam Lightning Beam (it lists a lower damage, but doesn't list DPS), and the last spell as Exploding Electric Icewall. Apparently my name for the icewall was almost the same as theirs, except it was more of a description than a name.
On the bridge, I used the super steam lightning beam to zap the enemies while they were far away, killing many of them, and then switched to using the exploding electric icewall when they got close, killing most of them without risk to myself (as long as I kept my shield up and stayed healed). It IS possible (but rare) to get knocked into the icewall or field left by it, and can be fatal if your shield is low and you don't have any kind of element resistance to, well, it does do four damage types, and I'm not clear on whether a cold shield protects against ice damage. The odds of that happening are extremely low, however.