Darren might be able to use the echo-location aspect of his vibration magic to let us get a clear picture of what their base looks like without going in, if he can do it without them detecting some kind of magic being used. If he can do that, Rutger might be able to remote-blast some stuff with Firaja, and during all the smoke and flames Artemis could cut his way in.

But I'm assuming there'll be various curveballs so the best plan is probably the ol' Monster Hunter's motto: Don't get hit, and hit it til it dies!