Orni is a female Egg Stealer Ornithiomimus. She first appeared in The Land Before Time XX: Tale of a Spiketail.
She is very cruel, at least for most of the 20th movie. It was stated that her parents broke up when Orni revealed that her father was cheating on her mother. Her siblings blamed her for the breakup and mistreated her after her father left. Her mother, while not blaming her, wasn't kind to her afterward.
Sometime later, a Sharptooth came and her mother, decidng that Orni was slower than her other children, and also having a grudge against Orni, left her to die, hoping to save herself and her nearer children. Orni was able to survive and got the Sharptooth's eggs for revenge.
She had since become unfeeling to the misery of others and had the motto that it was every Egg Stealer for him or her self. Her strong-will enabled that she was the leader of a gaggle of Egg Stealers of different sorts, despite such an alliance being taboo due to the seperation of the kinds that plagued all but the Bothteeth (omnivores).
Orni had even left one of her crew to be eaten by a Sharptooth when he tripped, but luckily for him, he was able to get out of there. Later, after a careless move of a member of her group alerts Ducky to their presence, Orni orders him to leave last, figuring that if anybody will get caught it will be him.
When he starts to mention too much, Orni throws a rock at him. After her crew member captures Ducky, Orni decides to spare her. This was, in part, as she thought Ducky's death would be too messy and attract too much attention, but also, because Ducky's soft demeanor awakened, albeit small for a good while, her better nature.
However, Orni tricks Ducky, under feign of caring for Ducky's fear of losing Spike and her dislike of her brother Derrick, into being a distraction that she hopes to use so that she can sneak eggs in the meantime, though Ducky does not realize this.