Shadowhunter was a female NightWing-IceWing hybrid who was mentioned in Darkstalker. She was one of the six possible dragonets that Clearsight and Darkstalker might have had in a formerly possible future.
She never existed in the timeline the books took place in.
The Jade Mountain Prophecy
Darkstalker mentioned that he and Clearsight were going to have dragonets.
The Lost Continent Prophecy
In the prologue, Clearsight thought that she would always miss the dragonets she would have had with Darkstalker.
When Darkstalker gave Clearsight a copper bracelet, Clearsight said that Eclipse would love it. Darkstalker was startled that Clearsight mentioned their future dragonets. Darkstalker thought that they would choose the name Shadowhunter over Eclipse for the dragonet, but Clearsight told him that Shadowhunter was one of the older siblings of the family.
= Possible timeline