Edward W. Robertsens cycle of Arawn and Galand are the main inspiration for the system of ether and nether, mirroring order and chaos.
Brandon Sanderson's worldbuilding in works like the Stormlight Archive is phenomenal, and has inspired me to make an attempt at it myself.
The Spellmonger Series by Terry Mancour shows a powerful vision of a medieval society, and it inspired me to incorporate a sci-fi element of humans arriving on an alien world in an otherwise medieval, fantasy setting. This also defends how humans come to exist on a different world, rather than evolution duplicating the feat on a different world - which is highly unlikely.
I've also borrowed the idea of a 'magosphere', and interpreted in my work as the 'etherscape' to explain how there can be magic on this world, but not on Earth where humans come by.
I forgot the name of the series, but it's something like 'a good dragon' - or something, in which a young dragon and a young magician work together in a world where magic has returned. It's a rather good series, in which the gods are slowly returning, starting with the natural spirits - and slowly the avatars of humanity's deepest fear and beliefs. The idea was that, with the return of magic, there were certain 'resoirvoirs' being filled with magic in an underlying landscape. The deeper the resoivoir, the greater the power, and thus the spirits returned first, because their resoirvoirs were smaller. I used this same principle in developing the etherscape, where common words or ideas carve deeper dents into the etherscape, and can be filled with more power.
The idea of Oration being a powerful means of using ether comes from the Dune series, by Frank Herbert, where Bene Gesserit order of women have the power to manipulate humans through speech. Granted, their powers are supposedly psychological and instinctual, not actual magic, but it is an idea that has stuck with me since. Besides the fact that the Dune series is absolutely incredible.