Hmm, I like that. I would pronounce the last syllable slightly differently from Artemis; like the last syllable in Christmas (not really rhyming with "miss" in my accent). I'm not sure I don't prefer it as ART-uh-mus or ar-TEM-us or some other pronunciation. Anyway, neat name, very neat!
I only think it "goes with" Ptolemy, not so much with Evening or Morpheus.