[quote=Nemaisare]
While I'm sure it can fix a lot of problems, humans as a whole are generally a quarrelsome species, and just because they have a quick fix to their problems (keeping it mind it might well not be as quick and easy as all that), doesn't mean they won't find reasons to covet [b]further power by position or what other people have[/b]. In fact, it seems to me like there'd be even more potential for trouble, with so many more options made available. It might actually be harder to uphold law and order when those you're trying to stop have exactly the same main weapon as you, and might well be better at wielding it. o.0 There are plenty of other motivations for killing and fighting other than gaining ressources for survival. [/quote]

Heh, you're quite a cynical person XD So, on one hand, we base these witches off the presumption that human nature is inherently evil and that there's a natural tendency to oppress or control, irregardless of the societal environment in which they were brought up. Then magic would just be a means to meet their ends - total domination, as without magic (IRL) its almost impossible to achieve such a scale of control. In this scenario, there has to be a really OPed coven thats wipes the floor with everyone. 
On the other hand, we have Covens made up of self sustaining individual witches that dont have to rely on outside influences. Their environment is such that each of their needs can be met pretty easily because everyone has a basic magical potential. This society will be magically different from ours, right from the start, if you imagine witches as a people close to the natural world, where their technology develops totally different from ours. Their idea of civilisation would be so different, theres so much potential to develop a unique society, completely separate from our own world. This society would be more interested in personal development and aggregation of knowledge rather than fighting among themselves. So, you see, their concept of power and control should be different as well because, naturally, when each Coven's needs can be met easily, through magic, there will be no ultimate power that can be imposed over them that would result in a war that makes both sides lose everything they have. (A real life analogy would be, why we dont just nuke the middle east or anywhere. Because they will nuke us as well and everyone dies)
TL;DR: All permeating magic gives humans the potential for more good, IMO... YES I'M NAIVE AND OPTIMISTIC! SHOOT ME!

But that doesnt really help the rp, So, maybe destroying other Covens give you more magic like you take their source of power but this power corrupts and make you wana kill more? The thing is, each house in GOT has their own motives, not just blindly killing everyone in the name of gaining power.

[quote] Although, admittedly, those are generally the most altruistic.I'm also hoping there's more restrictions on the magic to keep that sort of castle lost? *waves hands* New castle! from happening. ;)
[/quote]

How about singing magic? Say theres this sapling, and witches can perform rituals where they sing and coax the sapling to grow into whatever shape, eg. A tree that grows into a house while still being a tree that lives and grows. The restrictions would be time. Obviously, the growth is accelerated but it should take a week at least? for a normal sized house. Like in Eragon!