This first DLC is very… unforgiving. Also somewhat badly designed.
It’s split into two parts. The first takes place in a prison where you’re stripped of your equipment and hirelings, forced to do a semi-tedious ‘stealth’ sequence, and then fight through a bunch of enemies and two bosses using crappy white/green equipment. The second takes place in a fairly normal and decently sized dungeon with a large number of enemies to mow down.
The first half is brutal. Insanely brutal for any party that doesn’t have anyone that can cast Sleep and Burning Determination, and just normal brutal for those that do. The first problem is of course your lack of equipment. Depending on how you built your party (+Mana/+Health equipment instead of points in Vitality/Spirit) this alone can destroy you. The next is the status effects (Feeblemind and Sleep) that the enemies here can inflict on you; without Burning Determination Sleep will decimate you, and the only way to cure Feeblemind is with Expert Air magic or resting… and you have access to next to no supplies here.
The final problem is the two bosses. The first boss is an insanely beefed-up Blackfang Thug (he can cast 250+ damage Fireballs) backed by two slightly beefed-up Blackfang Thugs. Without Sleep or a full-Mage with something like Implosion this battle is extremely difficult and may actually be effectively impossible (with an all-Might party for instance). The second is a Mage who can put people to Sleep, casts a new Light Magic spell that deals 250+ damage to each party member, and even heal himself. He also gets a free action the moment you open the door.
If you defeat that second boss you can get your equipment back and return to the main world map. From there you now have the option of traveling to the second half of the DLC whenever you want (which is a massive improvement compared to forcing you into it as the first half did). The DLC’s second half is pretty straight-forward; kill everything that you see while exploring for loot. The only tricky part could be the optional Griffon boss, as it may Chain Lightning you into oblivion a few times.
I honestly can’t recommend using this DLC unless you only want to play with optimized Freemage-dependent parties and/or are willing to cheat past the cheaper parts of the prison section (by editing a spell/ability to do massive damage for instance).