[Questing for JUSTICE!]

A little sneaking, a spot of observation, and Cantata and Fayyaad find themselves ideally placed round the rear of the fortress. Parapets line the top of the fortress, providing a possible means to secure a grappling hook there, if they wished to do so. Alternately, the third floor window looks to have an opening that a well-thrown hook might be able to hit.

A particularly precise throw might see the rope line up nicely to give them a view through a whole set of windows on the way up, a possible means of gathering a little more information on what lies within, as well as providing several potential entry routes.

All in all, the fort looks like it has three floors to it, more spaced out than one might find in a typical building, suggesting quite high ceilings within. As Cantata and Fayyaad observe, there's a brief glow of blue light from the third floor, suggesting some sort of activity further in.

Meanwhile...

Wren distracts the cube! The cube slowly rotates to face him with an orange side. "Terribly sorry, my good man, afraid I didn't hear a thing! Rather poor form of me, eh?" The cube floats a little closer, somehow giving the impression of floating cheerfully, despite the lack of any particular features to speak of on its faces. "Still, no harm done. I say, are you here to deal with the ruffians inside? That'd be awfully convenient if you are. I was hoping to give them what-for, myself, but there's rather a lot of doors in the way. Bit of a bother when you don't have any hands!"