x xen species?

[Gordon-Shepherd]

in opposing force you meet two new kind of aliens that seem slightly related, but very different to the xen aliens. I believe the wiki referred to them as "the x species" or something? how are they related to xen, the resonance cascade, combine etc? also the last boss of op4, what is his relation to nihilanth/xen? he also seems to bear a striking resemblance to to those green tentacles you see throughout the game (just a side note) and where are the bullsquids, houndeyes, and alien grunts in half life 2? I could understand the combine wiping out the houndeyes and bullsquids, but wouldnt the grunts be forced to work just like slaves/vortigaunts?

just my 2 cents. sorry for the question deluge.

 

[ríomhaire]

They are only known as Race-X and they have no real impact on the story. Gearbox (who made OP4) made them up for new enemies. They are presumably from Xen too.