The Dark Ages takes us deeper into Giles' murky past. It soon becomes clear, however, that it's perhaps not quite as ominous as Lie To Me suggested. By the end of the episode, it seems that there's little more to be mined from this particular seam.
There's some compensation to be found in the palpable chemistry developing between Giles and Miss Calendar, the latter being given a lot more to do, including some fun scenes when she is in her "weakened state".
The return of Halloween's Ethan Rayne is no surprise, but it seems unfortunate that the producers seemed in such a hurry to bring him back. This episode is so muddled that it is unable to focus on the character, and what potential there was in having him return is lost.
The tension between Giles and Buffy is nicely played, culminating in the scene where Giles selflessly offers to take Buffy's place as Eyghon's next host.
The Dark Age is an important episode, especially for Giles and Jenny. It draws Cordelia and Jenny closer to Buffy and her work as the Slayer and leaves all the characters changed to some degree or other.