Arena bug, Paladin with Chameleos?

Hello, I recently played an arena against a Paladin and the legendary Priest card “Chameleos” was played twice, however there is no description of how we received this card, if it was an error or something because how are you going to have cards of other classes? I lost that game because of that and I ask for some explanation or something because it seems unfair to me.
Thank you.

Did they play anything like Prince Liam?

No, he just play Chameleos from his hand
http s://imgur. com/a/d SRig9t ( remove the spaces)