The simplest way to describe this episode is this: we had one question going into the Mortis trilogy, "What is the nature of the Force?". The first episode "Overlords" answered this question by leaving us ten more questions; and perhaps the second episode "Altar of Mortis" answered some of those questions, but left us with one-hundred more! I can only hope that we won't be left with a thousand questions after this trilogy concludes! Now to the details...
Story-wise this episode was both brilliant and slightly "out-there". It strayed from the events of the Clone Wars even more than the last episode. There was no Qui-Gon or Shmi to tie the story into the prequel trilogy, only the three main characters of the series cast back into the mysterious and perplexing world of Mortis. However by creating a whole new story arc independent from the politics and military excursions of the Clone Wars, the show has grown an environment perfect for something that many prior episodes have lacked, drama and suspense. In my opinion "Altar of Mortis" was not as insightful into the nature of the Force as its predecessor, yet I believe it held just as much if not more emotional energy. And like the first episode of this arc, it existed solely in this realm. There was nothing synthetic or mechanical about the portrayal of this story. It was an exploration of the characters reactions to extreme circumstances.
If by anything, this episode was painted by contrasts. The contrast of the selfishness of the Son and the selflessness of the Daughter was the most dynamic. While the Son was driven by a lust for power and control, the Daughter committed herself to humility and serenity. This served as both a microcosm and possible allegory of the Jedi and the Sith. The episode terminated in the Son grabbing for control and becoming consumed in rage, whilst the Daughter gave the remainder of her imperiled life to save Ahsoka. Another contrast was illustrated by Anakin and Obi-Wan's different ways of solving the dilemma of Ahsoka's capture. True to his impetuous nature, Anakin raced to the center of the problem in an attempt to solve it directly; meanwhile, conversely, Obi-Wan took a step back and sought out knowledge on how to rectify the situation. It can be argued that in this case both of these plans failed, as Anakin failed to save Ahsoka from the demon that possessed her and Obi-Wan only strengthened the Son by bringing the dagger out of its secured location.
This brings me to the most shocking moment of the episode. Even though we have been seeing production stills and short clips of "Evil Ahsoka" for months, how creepy was it to finally see her turn in full! Both the animators of the show and Ahsoka's voice actor Ashley Eckstein did a marvelous and haunting job of portraying the character in such a malevolent light. More-so than her malicious intents, the twisted way of speaking that Ahsoka acquired was highly unsettling. Yet on a more positive note, it was very exciting to finally see her wield her two lime-green blades! Also I would like to praise Matt Lanters portrayal of Anakin in this episode. The emotion in his voice was just as compelling if not more-so than Hayden's in Revenge if the Sith. Throughout the story Anakin's attachement to Ahsoka was highlighted, giving their relationship a great deal of depth.
As it has been for many weeks running, the animation in "Altar of Mortis" was phenomenal. The chase sequence at the beginning of the episode was breathtaking, as the Jedi's shuttle raced through the canyons of Mortis behind the ominous wings of the Son. The visual contrasts of light and dark are artistically stunning in the this arc, with the environment of Mortis deepening with each episode. The animation of the fight scenes in the story was also very well done, from the illumination of the Son's force-lighting to the choreography of the Jedi's dual. In addition to these amazing things the character expression continues to evoke realism in the series, from the proud aura of the Son to the twisted mannerisms of the possessed Ahsoka.
Finally I would like to address the relevance of this episode to the overall story of the Star Wars saga. The actions of the Son and Daughter certainly supported the nature of their characters, but did not really reveal anything more than what was revealed in the last episode. And it remains to be seen how material this story arc is. From an allegorical standpoint it illustrates the erosion of the power of the Jedi and the swelling of Darth Sidious' control of the galaxy, and literally it explains how these events happened. From what I hear from the creators of the series, this element will probably be left to our own interpretation. In my opinion the strongest accomplishment of this episode was in further illuminating Anakin's feelings for Ahsoka and shedding light on the vast differences between Obi-Wan and Anakin.
In conclusion this episode was very emotionally compelling and excellently animated. What was lacking in revelation was made up for in increased action and heightened suspense. It will be intriguing to see how this arc ends and what matters are resolved in this mysterious affair. For sure, if anything, the Mortis trilogy will serve to greatly deepen the characters of Obi-Wan, Anakin, and Ahsoka. But just as importantly, it provides the series with a story-line that is Star Wars, something that is exciting, causes anticipation, and makes us question what we think we know about our galaxy and the one far, far away.