Janus

Janus was an AncientsAncient who lived on Atlantis in the Pegasus Galaxy 10,000 years ago. He built a timeship out of a "Puddle Jumper" which was used by an alternate timeline version of Dr. Elizabeth Weir in her attempted escape from the flooding of the entire city of Atlantis caused by the expedition team's arrival. Janus' timeship crashed 10,000 years ago in the Pegasus Galaxy, but Janus himself escaped with the Atlanteans to Earth 10,000 years ago. It is possible that he created a new timeship in the Milky Way Galaxy and that ship was the one discovered by SG-1 on Harry Maybourne's planet.