Lu Yu

Lu Yu
Lu Yu is the mate of Danzi and the mother of Long Kai Duan.She was one of the original 12 imperial dragons that Master Lan kept at Huangling, the last to die in the pit. She died from misery.

Apperances: Huangling.
At Huangling, Lu Yu was most likely unable to fly and dull-colored ( Dragon Keeper page 5).She was a large and heavy dragon, as it was difficult to drag her up the steps after she died. To cover up the evidence and since the ground was too frozen to bury the corpse, Master Lan made dragon pickle out of her body.

Other times in Dragon Keeper:
When Danzi and Ping were walking through a city, the spotted a stall selling animal products. There is a dragon heart which reminds them of Lu Yu. She is also mentioned at Ocean, when Danzi tells Ping she must take Lu Yu's place as a dragon mother.

Garden of the Purple Dragon:
Coming soon.

Dragon Moon
Coming soon.

Trivia

 * The pickle Master Lan made out of her body is likely to be the cause of the former Emperor's death.
 * The dragon heart in the stall selling animal products  could have been Lu Yus.