Just forgot to mention that besides mages, ninja also uses surrounding aether in the form of mudra cast to perform their ninjutsu, they connect aether of different height so to say to perform magic-like skills. Precisely, the Ninja uses hand gestures to channel aether from the air and the ground through his/her own body and shape it into any physical form he wants or form defined by already established jutsus - so it would not be farfetched to invent new jutsus from a rp viewpoint. On the other side, it does not necessarily means the ninja uses his/her own aether to cast jutsus nor does he only deplete the surroundings of its aether. The way I understand it the aether may return to the environment after casting... but again if anyone has a thought to share about the special case of the Ninja I'm all ears as well ^^