Oneiros[54, 16] is a subregion of Feralas and adjacent to Dream Bough (one of the four entrances to the Emerald Dream). It has a small ruin and many many high-level elite green dragons make their home here. One of the Dragons of Nightmare (Emeriss, Lethon, Taerar, Ysondre) may also appear here.
The name for this locale most likely originates from the Greek myth of the Oneiroi, the sons of Hypnos, god of sleep. They were demonic personifications of dreams, and the most powerful of the Oneiroi was Morpheus, God of dreams. A fitting name for the realm of Ysera the Dreamer.