Perhaps not in the domain of "complex" numbers, but one method of visualizing various attributes is through layering of multiple dimensions.
For example, a scent, heat, or luck dimension can be extracted from and/or applied to the entities within a given spacial region.
Additionally, an entity may exist within a complex dimension whereby its X,Y,Z coordinates are only the visible representation and, as Xecutor mentions, additional dimensions of spirit, health, skill, elemental affinities, etc. are frequently present though rarely visualized as contiguous dimensions.
For example: the player's favor may exist as a point in the complex plane of a god's will, which is a field encompassing the combination of dimensions said god presides over, such as luck, vitality, vengence (critical strikeness), etc. Some sort of collapsed visualization of the complex plane may assist in informing the player of their current status even if it may be unclear to them how their actions multiply, translate and rotate them through the god's complex plane of consciousness. Perhaps a chaotic god could modulate their perceptual domain via
the Julia set to demonstrate a deterministic graph of their fickle nature.
Derivations of the players path within the complex plain of possible player statuses could be useful for automatic leveling of related stats. As for physically navigating in N+ dimensional space (keeping in mind that time is the unstated 0th dimension where "2D" and "3D" games are concerned)...
I have not yet demonstrated a sufficiently navigable display in my experiments, but I believe one approachable method may be rendering outward from the local dimensional origin rather than rendering the player's position from the global perspective. Rendering deviations from the local origin would have the tendency to show the immediate surroundings in the complex plane as more normal, and potentially more warped and strange the further objects are from the player's point of view. I've yet to implement this, however.