Bug or Intended? Gral + Spirit of the Shark.

It happenned in a casual game, where i'm playing the famous Sharkness combo against another rogue. I happen to get spirit of the shark from hallucination and played it turn 4, followed by 'Gral, The Shark' turn 5, who ate the darkness.

It was all good until my Gral got killed, resulting in no Darkness returned to hand. Because of the second battlecry activation 'eating' nothing, it might mean that it got replaced by the other minion of the second battlecry activation, which, in this case, was nothing.

If it is intended, Gral doesn't synergise with his own spirit. Poor guy.