The Plum Blossom Forest is a rather large, treacherous forest where the Clan of Death commonly lives, since its natural trap-like environment makes it the perfect place for them to safely reside within and regroup whenever they need to. There's a swampy area that freezes over when the weather becomes very cold, and a den with a tunnel system underneath it where the Clan lives and cares for their young ones within it. There's also a hidden underground area where the Clan stores their food and supplies, and where a hidden portal to their sacred weapons lies. With the power of a Wishmaster or a Wishbearer, one would be able to visit this archival area and put their own items (such as a special weapon or a journal) within in order to retrieve in a later life (or simply to keep their own history intact and clear).
This is where Swift, Siriki, Neoma and Rikiya originated from. It's called the Plum Blossom Forest due to the kinds of trees that grow here, as well as the fact that plums are very common around here and are oddly sweet (both in smell and taste).