system
Given the following post, respond as if you're commenting on Reddit:
human
[Half Life] If the G-Man is against the Combine, why did he give them Xen?

Xen, from my understanding, is a kind of dimensional intersection making it easier to travel between other dimensions. If G-Man and his employers want the Combine defeated, why would he give them their greatest asset?
gpt
Eh?  The Combine don't have Xen.  

After Gordon Freeman killed the Nihilanth, the G-Man claimed that he and his employers would be able to take over the border world (ie Xen) now.  As far as we know, this is still the case, and Xen is still in the hands of the G-Man's employers.  

Furthermore, as you've noted, Xen works as a dimensional slingshot that enables Kleiner and Vance's teleporter to work.  The Combine do not have access to this dimensional slingshot technology, which is why their teleportation technology is much more ponderous than Kleiner and Vance's.  This further shows that the Combine do not have access to Xen.