Yes, I knew they cut it out, because I was waiting for it the whole episode *sighs* Marie told us, it was for ep 6.

I think they cut it out, because evil!Merlin was using magic... I think they decided later on that he wouldn't use magic while possessed by that thing. Still, it's such a shame! ;o) I really hope they'll put it on the DVDs as a deleted scene, I mean, they spend an entire day on that scene. ^^