Plane Projection
The process of creating and maintaining a subplane outside of one's soul, often within an ichor-based enclosure. Within such a construct, often called a soulplane, the engram encoded in the ichor is local law; this could be a certain space-time metric, an immersive memory, or various other phlogistic effects.
However, the more complex the encoded engram, the more difficult it is to stretch the ichor without tearing it. Thus large or complicated soulplanes are yet further difficult to produce. This is made worse by the fact that as more soulfire is contained within the plane, the ichor barrier must be made larger.
Countermeasures
Once inside a projected soulplane, escape is extremely difficult for any who are not rather familiar with ichor manipulation themselves. Spatially, a soulplane is often projected with a differing volume density and toroidal topology, thus the only way out is to directly attack the composing ichor. This is tantamount to rending the fine threads of reality, a predecessor of the same skill which allows one to deploy a soulplane in the first process, and one that is resisted simply by strong ichor.
As Soulplanes
Notably, the actual soulplane--which is the interior conscious plane to the soul--is separate from a projected soulplane, which can differ wildly from the creator's actual soulplane, but also may indeed be a distinct copy of it. In fact, soulplanes which constitute an exact replica are often noticeably more durable due to their alignment, at the cost of a fixed and uncontrollable effect based on the user's cognition.
Open Plane
While exceptionally rare, with only a few individuals in recorded history accomplishing this feat, it is possible to maintain ethereal ichor without an external barrier. Such planes lose the benefit of topological manipulation, but are functionally impossible to destroy without advanced knowledge of the techniques involved, as one cannot rely on collapsing the enclosure to destroy it.
