Just synthesizing some points we know:
There's a tech room entry that goes by The Vishnans - What We Know. Looks like it's written by the GTVI. In it, it states that the Vishnan Great Psyche is an entity in subspace (this is also stated in the debriefing for Act 3's Universal Truth). The tech room entry also states that
subspace surrounds all universes. We know from the Ken mission that the Vishnans maintain the
walls. What are walls? The thing that surrounds something else. The Vishnans therefore maintain subspace itself.
Not only do walls keep things out, they keep them in. This is supported by the entry for The Great Darkness which hypothesizes that humanity lives in a quarantine zone of some kind.
The tech room entry also states that from subspace, the Summed Psyche entity ought to be able to observe all space-time in our multiverse in some limited manner. The data packet for Shivan Origins state in Shivan mindspeak "selective pressure for resumption of panoptic function". What's a panoptic entity we're aware of? The Summed Psyche. Furthermore, panoptic can also refer to a
certain design of prison or institution. The data packet for The Great War stated in Shivan mindspeak "retrajectorize for mass upload to safe strata", which I take to mean influence the Humans and Vasudans so they become ready to enter the Summed Psyche. The conclusion is that within our multiverse-prison the Gardeners (Shivans), by the direction of the panoptic observers (Vishnans), attempt to cultivate life capable of meeting the requirements (enlightenment) to enter the Summed Psyche. This system and the rules it follows (Protocol) was set down by the Brahams, but is now failing.
edit: OH. Just had a revelation about the "selective pressure for resumption of panoptic function". This is from the Shivan ORIGINS module, which displays their mindspeak as they entered our multiverse. We know the Shivans preceeded the Vishnans. We know the Vishnan Summed Psyche now fills a panoptic function. Maybe this shows the Vishnan origins, as a species who were cultivated by the Shivans into developing their Summed Psyche, so they could fulfill this objective.