TIME BASTARD - A REVIEW
The premise behind Time Bastard is that time travel cannot be used to create duplicates of entities. It is possible for past and future versions of entities to exist in the same point in space-time, but duplicate entities from the same time period cannot coexist. The doubles in Chrono Cross do not violate this because Home and Another are separate dimensions.
Consider this scenario:
At the Millennial Fair Crono warps 400 years into the past. His presence in 600 AD creates a new timeline, and the original is sent to the Darkness Beyond Time. In the new timeline, a new version of Crono will exist, but the original version of Crono in 600 AD is not affected because he has time traveller immunity.
In 1000 AD, the new version of Crono may enter the warp to 600 AD, but where does he go? He cannot arrive in 600 AD, because the original version of Crono, who is protected by time traveller immunity already exists there. Based on evidence in Chrono Trigger, time periods do not fill up with duplicate time travellers. Thus, the new version of Crono is eliminated from the timeline and sent to the DBT.
Basically, if changes to the timeline result in the version of a time traveller entering a time-warp not being identical to the same traveller exiting the warp, the traveller entering the time-warp is sent to the DBT.
And if Crono continued time travelling:
The original version of Crono warps from 600 AD to 12,000 BC, creating another timeline. Yet another version of Crono would enters the warp in 1000 AD, and is sent to the DBT. The original version of Crono, protected by time traveller immunity, arrives in 600 AD. However, due to the new timeline, when this version Crono warps to 12,000 BC, he is not identical to the original Crono, and is sent to the DBT.
Another case:
Perhaps if the changes to the timeline are severe, the new version of Crono would not enter the warp in 1000 AD (or the version of Crono in 600 AD). Would the original version of Crono return to the present to find a duplicate of himself? Since there are no duplicates, the new version of Crono must have been sent to the DBT at the same time the original Crono left.
The Theory in a Nutshell
Duplicates of entities cannot be created through time travel because this would violate the conservation of energy in the universe. If a time travel scenario would cause a duplicate entity to exist, the entity with the least seniority of time traveller immunity would be sent to the DBT.
Examples
Robo encounters the past version of himself in 600 AD
After Fiona's Forest is replanted, Robo warps from 1000 AD to 600 AD and encounters his past self. They are not duplicates because the versions of Robos are not the same age. They are the same version of Robo looped in time. When the "past" version of Robo reaches 1000 AD, he will be sent into the DBT at the time the "present" version of Robo originally warped out.
Magus encounters Janus in 12,000 BC
After the encounter with the time travellers in 600 AD, Magus is warped to 12,000 BC. Magus encounters his past self (Janus), but they are not duplicates because they are not the same age. During the destruction of Zeal, the new version of Janus will be sent to the DBT at the time the original Janus was warped to the middle ages. The new version of Magus will be sent to the DBT when the original warped to 12,000 BC, and so on.