I'm not sure about story elements as I believe all stories are invariably iterative and inspired by every other media the writer has consumed.
I'm also not really ashamed of these, I recognize inspiration has to come from somewher, and in spite of inspiration I take nothing from characters that are not mine.
Azreth was inspired by Acnologia from Fairy tail, though their motifs are diferent they are still black and blue dragons that eat magic and dispense lots of pain. And Azreth's kin form (aka humanoid form) is also fairy tail inspired, but mostly by gajeel.
His dragon form however is completely different from acnologia, I just do not have artwork for it, but let's just say he is much chonkier.
You can check the resemblance yourself, images (that are not Azreth) are courtesy of google.
I could also say Vernon's power was passingly inspired by the power of a character from fate/stay night, most precisely Shirou Emiya.
Albeit their powers are completely diferent in how they work and what they do, I can say they bear some similarities that could make it seem like they are doing the same thing, but we will go into great detail on vernon's power inside the plot.
I would not say I inspired, so much as I made an homage to McCoy from the desperados series, I actually made a Grey's mentor figure to be mostly like a furry version of him as I love the character. Though I did give him an original background and look.
In spite of that detail, Grey is original, and he himself is not actually inspired in any 1 character, but I could say was inspired by every 'low magic' character in a world full of spellslingers, ever, It's just a neat concept and makes for some great fights to have a character whose sole power is their foresight.