Zweilous first appeared as a Deino when Lexi and her friends arrive at the Strange House outside Lentimas Town. The Deino was trapped in the Strange House, which Lexi and her friends managed to save from. Afterwards, the Deino showed an interest in joining Lexi, which he did so. Afterwards, Deino was trained to a level where it was able to battle against Drayden and draw, despite it's low training level and its type disadvantage. Afterwards, it was used against Marlon at the Humilau Gym.
During Lexi's traveling through Victory Road, Deino's training stepped up a notch to the point in which it evolved.
Zweilous first appeared when he was used against Caitlin at the Unova League in B2W2-053. Zweilous had a great source of new power due to the evolution, which spurred him to want to evolve again in the future, but only after he was completely in control of his new strength.
Zweilous as a Deino was quite clumsy and lazy, even though he would pay strict attention to the battle when in one. As Zweilous, his clumsiness continued however he became much more active and less lazy.
As a Zweilous, they try their hardest to live up to the reputation of Hydreigon. Zweilous might fight alot with each other, but their intimidation is unparalleled.