Mother
This baddy is the god of the bug people, supplying them with the juice of life.   Turok2 producer Dave "Decapitation" Dienstbier quotes, "That's what I like to hear" after he heard IGN64's staff taking off.
Golden Eye
Where to start with this guy?   Well the first thing that comes to mind is that the game sucks, but about the guy, he's essentially a huge golden eye staring down from the ceiling of a cave.   Tentacles come out from all sides trying to do stuff to you, maybe even harm you !   Over-loaded transparency affects create a visual treat while playing this crappy game, er fighting this creature.
Mantid Boss
A huge mantis living in a polygonal environment, spewing eggs which hatch nasty bugs, who run at you.  'Nuff said.
Primagen
This guy is supposedly the root of evil.  With a name like that, that prima part, like primary, he sounds like he is.   Impotent sources tell us he's a cross between a cockroach and a mantis.   Technology will still show it's ugly face, being as how this dude crashed in a UFO.   Unlike that He-Man like Campaigner guy, this one is big.