The reason for war is a wisp that serves as the focus of a memory of Nomad in the Tales of Nomad miniquest. It may be interacted with in order to spawn the next Nomad's memory, which will provide a cryptic hint as to the location of the next A memory.
This memory depicts Nomad outside the Soul Wars waiting room and inviting people to play it, in order to bolster his own power.
The update history project is a work-in-progress – not all updates to this topic may be covered below. See here for how to help out!