I think i might detected a bug in heartstone.
I put a Rylac Metalhead next to a golden Reverber drake, during battle my Tarecgosa got tons of echoing roars, but they did not take effect. When hoovering the card i could se they had been placed, but the effect of it never happend. The same goes for my other dragons that was next to my Persistent poet. They alsow got and keept the echoing roar, but the effect of it never happend.