Black Omen (Monsters within)
Inquiry
What's with the monsters at the Black Omen? You can go through it three times if you start in 1000 A.D. and work backwards, yet some monsters you can only fight once. And what's with the souped up Lavos spawn?
Answer
The enemies in question are the Lavos spawn, the Mutants, and the Laser Guards on the outside. In all probability, their disappearance after one battle is a result of their event programming; as bosses, they were given this condition without a second thought. However, a viable plot solution does exist. Notice that the Lavos spawn and the Mutants all seem to unnaturally appear; the Lavos spawn even comes out of a Gate. This means that they were not always present on the Black Omen, and instead came from somewhere else (for instance, the spawn may have come from 2300 A.D. at Death Peak). In this case, they could only travel to the Black Omen once; if they were defeated, that's it -- they've exited their home periods and died, leaving no further versions. This theory only encounters a problem with the Laser Guards, who exist normally on the outside of the Omen and do not appear after being defeated once.
Concerning the Lavos spawn, it is interesting to note that it is considerably stronger than the ones encountered on Death Peak. This is most likely due to the time that has passed since the heroes ascended the mountain. In the future, the Black Omen could take the strongest spawn to have matured thus far and transport it to fight the party. This is also consistent with the theory of a one-shot transport above; until the Black Omen were defeated once, it would still exist in the future.
From: Common Questions