The Time Devourer as a Product of Lavos' Pocket DimensionThe generally accepted definition of the Time Devourer is the merger of Lavos and Schala in the Darkness Beyond Time (DBT). Lavos exists there because Crono defeated it in 1999 AD, sending the ruined future into the DBT. Schala was sent into the DBT after being caught in the dimensional vortex surrounding Lavos during the collapse of the Ocean Palace.
However this presents a problem. Every time the travelers warp through time, another version of Lavos is sent into the DBT. The same goes for Schala. Each time the travelers warp to 65 million BC, another version of Schala is sent into the darkness. This creates dozens of potential Time Devourers to threaten all existence. We know, of course, that there could only be one Time Devourer.
Also consider this:
Belthasar: The Devourer of Time is a new life-form... Born out of the fusion of a life-form from this planet with Lavos, who nests on the far side of the dimensional void. In the far-off future, when the fusion becomes complete, IT will awaken... Then, the Devourer of Time will begin to consume all space-time continua... Despair and hatred... To return all things to nothingness... That is what IT desires. Here... Take this with you.
Was Lavos inside the Darkness Beyond Time, or beyond it?
By applying the pocket dimension theory to the Time Devourer, these problems are easily resolved.
Lavos exists within a pocket or warp in space-time, which is connected to all time periods simultaneously. In the pocket, time flows along an axis perpendicular to the normal timeline. Thus, as time passes within the pocket, to any external observer Lavos is unchanging for all time.
Within the Pocket Dimension, Lavos is unaffected by any changes made to the timeline of the outside world. Only when Crono enters the pocket itself and destroys Lavos there, is the pocket dimension timeline altered. In the new timeline, the pocket dimension simply collapses, but the original timeline containing the future version of Lavos is cast into the darkness, pocket and all.
Since only one Time Devourer ever existed, we can confirm that the TD did not arise from changes to the normal timeline. If Lavos exists outside the pocket dimension after 1999 AD, eliminating the ruined future does not create a TD. The pocket dimension theory provides the solution, so long as we surmise that the TD originated from the pocket dimension within the DBT. There was only one version of the pocket dimension in the Darkness Beyond Time.
We must also consider how Schala came to be inside the pocket dimension with Lavos.
As the palace collapsed around her, Schala was sucked into a dimensional vortex along with the Lavos Mammon Machine.
This can be taken to mean that Schala was bodily transported into the DBT, or that she was caught up in Lavos' pocket dimension as it erupted through the surface. In both versions of the Ocean Palace disaster, she would have been consumed by the living version of Lavos inside the pocket dimension. However, by defeated Lavos in the future, Crono changed the past as well.
Since the "present" state of the pocket dimension is static for every time period; for all time, Lavos is frozen in the Darkness Beyond Time. Instead of being devoured by Lavos, Schala is pulled into the eliminated pocket dimension inside the DBT. Because Schala retains existence in the DBT, it is possible that her presence revitalizes the frozen pocket, giving Lavos new life. Schala and Lavos would slowly merge in the perpendicular timeline of the pocket dimension, and when the Time Devourer was complete, the destruction of the universe would occur simultaneously throughout all time.