The Time Devourer. Wasn't the Dragon god just a projection of the TD's thoughts? I guess if the Dragon god had been previously consumed by Lavos's power, it is posible for the TD to use it's physical form for it's link into reality. That means that when the Dragon god was split, it was actually the TD using it's form. By the way, what was used for Serge to enter into the Darkness of Time? If I remember correctly, the portal was only open after the Dragon God is defeated and the Tower falls. Could the death of the Dragon God caused the tear in the dimentional rift between reality and the Darkness of Time? Also, the Frozen Flame was a shard of Lavos, yet it has it's own ability to think and corrupt things around it. Doesn't that make them the same being it two seperate forms? Finally, what did the Chrono Cross have to do with destroying the TD, I know it had to be used in conjunction with the other elements, but it was made using the broken dragon's tear from each dimention. Where did the dragon's tear come from and who could've known to make an altar where two shattered pieces could be reunited? It's been a while since I've played either of the games, but I think I know what I'm talking about.
Just as a side note. Harly's name in Japanese is Tsukiyomi, correct? I know that Tsuki = Moon, as for yomi, I'm not sure. It could have some connection between her and the Dark Moon Dragon.