Eclipse never existed in the timeline the books took place in.
The Jade Mountain Prophecy
Darkstalker mentioned that he and Clearsight would've had dragonets including Eclipse.
The Lost Continent Prophecy
In the prologue, Clearsight thought that she would always miss the dragonets that she would have had with Darkstalker.
When Darkstalker gave Clearsight the copper bracelet, the same object later used to put him into eternal sleep, Clearsight said that she loved it, and Eclipse would need it the most. Darkstalker was surprised that she mentioned their future dragonets and remarked to her that he thought they would choose the name Shadowhunter over Eclipse for the dragonet. Clearsight then told him that Shadowhunter would be one of their other daughters they would have. Before Arctic was killed by Darkstalker, Darkstalker and Clearsight spoke together about their dragonets, and Clearsight said 'Eclipse, Shadowhunter.'
Clearsight had a vision where her and Darkstalker showed Vigilance their dragonets. Clearsight also saw a vision where Eclipse was chasing Queen Vigilance's grandson around laughing and Vigilance put on a rare smile.
= Possible timeline