So the originals were named after the Greek gods of Dreams and Night Terrors, so I figure the new ones I could name after the Roman Gods of Sleep and Nightmares, Melinoe and Somnus. That could work.
Aww, I can see Shiro's heartbreak now. He, Oswald, and Robert somehow retrieve it without dying. Then he goes to deliver it and only finds out she's already moved on and created a new pair. Shiro secretly hiding the old pair without ever saying anything.
-Sighs dreamily-...WE NEED TO MOVE THESE FREAKIN' MISSIONS ALONG ALREADY XD