Since after the event of Season 4, Spike agree to take care of the Mane 6's pet while they go to help Twilight get used to the new Friendship Rainbow Kingdom. During one point when the pets went on a mischief, they all accidently cross a new and ancient mirror hidden deep in the Canterlot Castle to a new world and transformed into anthropomorphic version of them themselves and able to talk.
Soon when Spike got captured by a ancient evil known as the Dark Tribe with along the rest of the legendary heroes, Angel and his pet friends encounter Lavertus who then discovered that in order to face against the Dark Tribe, legends foretold that 6 legendary knights will return in a incarnated form of 6 animals to save chima. Now gear up with new armor, weapons, vehicles, and powers, Angel and his friends must now fight to save the legend beasts, the legendary heroes, and Spike from the Dark Tribe as 'The Knights of Chima'.