Pretty straight forward issue. The Chimera doesn't count as a card for the purposes of discarding for the Almalexia Patron cost. Almalexia couldn't be activated in this scenario. After trading Chimera for a different card, I was able to use Almalexia's button again.
Don't tank
"In future content we will probably adjust this model somewhat (The BOP model). It's definitely nice to be able to find a cool item that you don't need and trade it to someone who can't wait to get their hands on it." - Wrobel