I am just not entirely sure. After he comes back from Hell, Betruger no longer acts like himself - he acts like he is in fact the Devil himself. In charge. The demons are HIS children, and he orders them to do everything - "Stop him!", "Kill ALL who oppose me!", "My guardian will destroy you!", etc. The Guardian example is particularly good, as the guardian is implied to be ancient, a demon having existed since the beginning of time, far predating Betruger - but not the Devil.
Another weird thing about Betruger's story is that he made a deal with Hell... and Hell honored it. No catch, no Faustian bargain. The dude just wanted to be a big demon dragon with spooky necromancy powers and Hell said it'd make that happen if Betruger helped it invade. Hell didn't betray him on general principle or try to punish him when his invasion plan was a total failure, not even in a monkey's paw careful-what-you-wish-for way.
Betruger seems to be living it up in Doom 3's ending, not suffering, and in the expansion he's totally happy with his new job and new body. If not for the second marine blowing him up, he would have faced no negative consequences for selling his fellow man down the river Styx. The Pit was portrayed as being more honest and equitable than most government officials.
The idea that Betruger made a deal is only confirmed by secondary info - someone from id involved in the development of the game said that. The game itself seems to paint a different picture, one of an obsessed scientist who entered the portal initially to disprove all the hub-bub about the other side being Hell when he would come back perfectly fine. Instead he gets possessed by the Devil himself when the demons realize he's the one in charge of the teleportation experiments, and has the access needed to bring the Soul Cube back with him - opening the gates permanently.
I personally believe that when Betruger came back, his original personality and motives were already gone and he was now a puppet of the Devil, doing nothing other than what was necessary to open up the portal. Once it was open, he went back to Hell permanently and transfigured into a grotesque beast.
PS: The idea of retro-looking technology being used by drastically advanced societies isn't unique to Doom 3. It also occurs in the Metroid universe, with the Chozo whom, despite being a post-singularity species, build "stone" statues (which are apparently actually biotechnology of some sort), live in ancient ruins built by their forebears, etc. The games make explicit reference to this and their reasonings for it - their belief that a balance between technology and spirituality/naturalism is necessary.
Last edited by Quasar on May 15 2013 at 18:39