==Contains minor spoilers==
This was a fun DLC. It is very short though. The map design is a lot more fun combat-wise compared to previous campaigns. For instance there are places where to duck and take cover. The fights are often intense, but still doable with two players. But you need to be pretty familiar with the game. We did not find any spells except haste. Might be a few other spells hidden there somewhere. For us, the boss fight was the highlight in this DLC.
I believe Dungeons & Gargoyles is a sequel. I have not bought it yet.
That said, the DLC is very expensive if we take nothing else into consideration. I would not buy it at less than a 75% sale.
If we take other things into consideration, whoever is behind the sales of Magicka are generous. You can often find Magicka in cheap bundles, sometimes with DLCs included. So if you got your Magicka for instance on Humble bundle, then buying this DLC is no big deal.