And your TGish desires are answered by none other than Hild herself, who if you didn't know, and this is a spoiler...
...is the mother of Urd, and obviously, God's lover or wife (not sure) at one point, otherwise Urd wouldn't exist.
...anyway.
So the demons in this series are more michievous and self centered than hardcore disgusting and evil, but they are demons.
So suppose Hild offers you a deal... you can get TFed into whatever form you desire, but from that moment on for eternity, you are one of her "employees," that is, a demon. Now if you know something about the AMG world you can pick a specific role, but none the less, demon / demoness you will be, and there is no save from any of the godesses, and you can't break the contract.
So... will you or won't you?
http://www.goddess-project.net
The conflict between the gods and demons does not seem to be political or idealogical in nature. Instead it seems to be based on something more simple and basic. The gods have the most control over Yggdrasil (and its power over our reality) and the demons want that power for themselves. Mostly because they just want power, in any form.
To clear up some possible confusion, Yggdrasil itself is neutral. It just keeps recreating our reality over and over according to the rules it was programed to follow. In order to alter this reality according to their wishes, the demons have their own system, Niedheg, that interfaces with Yggdrasil and instructs it to change what it's doing in some way. In order to counter this, a god or goddess must first crack the security codes Niedheg and/or the demons put on these new instructions so they can order Yggdrasil to change things back. (Demons must do the same thing to break a god's magic spells.)
The gods are doing the same thing when they use their powers, except their interface system hasn't been given a seperate name. This may be because it's so intrinsically related to Yggdrasil the gods see it as one system (or Mr. Fujishima never got around to naming it). Anyway, the gods have the most control over Yggdrasil and the demons don't like it. So their agenda is to get as much of Yggdrasil's functions routed through Niedheg as they can and reduce the number of transactions the gods control. And to do that they'll grant wishes to any mortal they can con into it while trying to undercut any god or goddess transaction they can find and force the god or goddess to return to the heavens. (That's what Mara's mission is.) In other words, they want all the wishes (program modification activity) to go through Niedheg, thereby reducing the god's control of Yggdrasil.
Some renegade demons have taken this desire to an extreme (ie -the Lord of Terror's plan to destroy Yggdrasil and replace it with a new system of its own creation.), but for the most part Niflheim is content with the conflict the way it is. That's because demon society would probably fall apart if they ever did defeat the heavens, which is one of the reasons the demon leaders (who ARE smart enough to see this) restrict their operations to just countering the gods' and goddesses' activities in our world and not pressing the fight.
So essentially, we're a 3rd (dimensional) world nation that two foriegn super powers are fighting their war of dominence in so they don't mess up their own countries. For the most part, we locals are unaware of what's going on, although the fighting occasionally affects us. And both sides have an ongoing campaign to win the hearts and minds of certain key locals (wishes) to extend their control over events.