The show was infamous for coming up with intriguing ideas, but never really doing anything with them the Skrills are cloned, then they have a queen which is set loose in the rain forest to reproduce freely before transforming into a glowing butterfly creature. A major supporting character suddenly became the central protagonist, and the Taelons were replaced with a much less ambiguously villainous species. Infamous for its final season, which radically altered the show's cast (again) and very premise to the point of it being more like a Spin-Off. In a lot of ways, it was like V (1983) only much more complex and with no clear good guy, bad guy or motivations. The second main character also was an alien hybrid. And it turns out to be a lot more complex as both species are intertwined into some extremely vague purpose and need each other for survival. The Taelons aren't outright evil at all, the Taelon characters are as diverse in how evil they are as the human ones.
The alien species in the show seem even more divided than humans in their political goals and even more so in how to achieve them.
It takes Always Chaotic Evil, tells it it sucks, and then throws it through a portal into space. Naturally, it turns out that the Taelons have a hidden agenda. They have since removed all hunger, war, and societal ills from our planet, but a human resistance movement (known, appropriately, as The Resistance) essentially wants to know the price-tag for all these benefits. The series starts by showing us it has been three years since a Sufficiently Advanced Alien race called the "Taelons" arrived on Earth. It's also one of the few series to kill off its lead after the first season. As the title might suggest, it takes place on Earth, a very lethal place as many characters die swiftly after being introduced.