This is a neat short adventure for a mid- to high-level party (11-13). It is well presented, with good atmospheric illustrations and clear layout, putting everything just where you want it when you settle down to DM.
The plot is quite straightforward: in attempting to regain territory in the Underdark, the civic leaders of the dwarven city of Karn Ungil have determined that it will be necessary to capture a certain fortress, one in which many magic wards lie dormant but which can be activated to their advantage. They'd appreciate it if the party would provide an escort to the spellcasters trained for and tasked with the activation process.
Naturally, nothing is as simple as it seems when you interview for the job!
It is playable as a one-shot, or may feature at an appropriate point in an ongoing campaign. There are plenty of suggestions for expansion or continuation, and - particularly if this is a one-off - one or more of your players can be given the roles of the specialists that everyone else has been hired to escort.
Each combat encounter is laid out clearly complete with map and full details of the opposition including likely tactics as well as their stats and capabilities. The whole thing is atmospheric and nicely-constructed, at no point do you feel that a particular creature is where it is merely to provide a fight, a pleasing air of realism pervades. Whilst the main focus, as you'd expect with an escort job with a warlike air, is combat there is still scope for role-playing interactions along the way.
Enjoy this combat-heavy claustrophobic venture trough the Underdark, with sufficient twists to keep the most alert character on his toes!