"There are too many Varricks!"
After promising earlier this season that tech using the spirit vines would change everything, Varrick has continued his experiments with Zhu Li. While the end goal is still unclear, the genius engineer is attempting to store the energy from the vines into batteries. In line with his eccentricities, he has named the units of measurement for this power "Varricks" (units of weight are measured in "Zhu Lis" apparently).
An explosion resulting from the experiment causes Varrick to question his work, something Kuvira won't allow. Using the metal from his uniform, she threatens his life if he refuses to continue. Why do these people wear all this metal when their boss is Magneto? After a failed escape attempt (but awesome mecha fight), Zhu Li allies herself with Kuvira, Bolin is sent to a re-education camp, and Varrick is forced to continue his work. What that work will result in is a big question, but the blast from his failed attempt did resemble the spirit energy from Vaatu in Book Two.
Zhu Li declaring herself to be allied with Kuvira is harder to read into than it would appear. After a tender moment between her and Varrick earlier in the episode, it would seem obvious that she would say whatever she must to stay near Varrick. And working at Kuvira's side puts her in a pretty powerful position (and it probably a lot nicer than a re-education camp). Still, when turning against her now-former boss, she complains about his treatment of her, and it's entirely valid. Varrick is a self-obsessed jerk and is constantly rude to Zhu Li, even in that tender moment they had earlier in "Enemy at the Gates". She could be legitimately loyal to Kuvira or secretly committed to Varrick, neither would be a surprise.
Mecha in Avatar:
Mecha tanks aren't something new to Legend of Korra, but the mechanized suits used in Kuvira's army are vastly improved over the ones used by Amon's Equalists in Book One. Not only are they smaller and more mobile, they are packed with hardware that allow for some inventive fighting.
It's the first big fight sequence of the season and was definitely the best use of the mecha tanks in the series. ATLA and LoK deliver some of the best combat when the benders are being creative with their abilities, and the new gear on these bots allows just that. Zhu Li - who is always perfectly capable at anything she does - holds her own against the trained soldiers and pulls of some great moves. Resorting to earthbending, Bolin leaps out of his suit and pulls off a few creative tricks of his own, including dropping a tree on his opponent.
The digitization of the scene was obvious, but if the rest of the season includes fight scenes choreographed this well, we're in for some great moments, especially when the major players (Korra, Kuvira, maybe Toph) get involved.
Bottom Line: The first big fight scene of the season is a blast, and the episode sets the tension for next week's "Battle of Zaofu".
Recommendation: Not a game changing episode, you can skip this one, but why would you? It has a ton of Varrick scenes and an awesome mecha fight.