What richness in action, what grandness in character! This episode, while not perfect, is a real treat, and finally brings the gang and Azula and her team together. Aang once again has to fear for his and his friends' safety while pursuing his task of finding another earthbending teacher.While this episode also follows two plots to begin with, they eventually merge to become the very first meeting between the gang and this season's villain. On the way, we get a lot of nicely done characterization of Azula and her, if you can call it that, friends.Aang's side of the story is not too interesting in the start. In his search for Bumi he frees Omashu, and while the pentapox scenes are somewhat silly, they are probably a good balance to the much darker second half. The princess' part of this episode is much more engaging, since we are introduced to two additional characters, Ty Lee and Mai, who, both in terms of personality and skills, are bound to add some color to the show. And from their fighting, they do seem to fit an elite team, as Azula puts it. Things are bound to get exciting.Azula herself is further characterized by her actions. Her ruthlessness does not seem to end at her enemies and subordinates, but she can be brutal and manipulative even to her friends. Which makes her relationship with Mai and, especially, Ty Lee, very layered and difficult to pinpoint. This also means that Azula as the villain is now being revealed to be more and more dangerous, a challenge the gang might not be able to overcome.When the two groups eventually meet, we get some very nice action, and the show keeps its standard in terms of making the fighting artistic and aesthetic. I particularly like the part where Katara blocks Mai's shuriken with a board. We also find out Mai's and Ty Lee's abilities, and their lack of bending adds a new element and more complexity to the otherwise elemental fights. Azula especially once again displays her prowess, and boasts with excellent bending abilities along with great martial arts in general.When Aang finally gets to talk with Bumi, we learn that Bumi will not teach Aang earthbending, but instead someone who "listens and waits". Since the show hasn't really presented that many named earthbenders, this can only mean that we can expect a new main character to be added to the show, and the gang.The scenes with Tom Tom were a nice reprieve from the otherwise heavy-duty stuff that went on in the rest of the episode. Sokka and Katara handling the baby by the campfire created a very humane atmosphere, something that can truly be related to in an otherwise flashy and fantastic world. The very end, where Aang returns Tom Tom to his parents ended the episode on a happy note.In terms of music, this episode also has its fair share of goodness. In the resistance base, we get to hear a modified version of the majestic Omashu theme first played in 'The King of Omashu'. But much more than that, Azula's very own theme, a heavily modified and scary Fire Nation theme, fits her spot on, and creates just the right feel whenever she appears on scene.In conclusion, 'Return to Omashu' is the start to a serious tone that might very well stretch through the rest of the show, and thus make it just that much darker. For me, that's just what the show needs. Not that I don't mind the jokes, but the real excellence of 'Avatar' comes from the writing, the characters and the plot, and if things get more mature and serious, I trust the writers enough that it will turn out great.