Board Thread:Show-Related Questions and Answers/@comment-26116863-20151117024202/@comment-25926288-20151117142015

For the tethering debacle, I think Emma used her Darkness-riddled HG magic and Excalibur to remove Merlin's HG magic (Which is why it looked like the Darkness was coming out of him) and corrupted it with the Darkness and put Darkness-riddled HG magic inside Hook. Emma used the Promethean Flame to untether Merlin.

So, like this: (Both processees concurrent)

Emma---(Promethean flame)>Untethered Merlin

Emma---(Darkness-riddled magic)--->Pulled the HG magic out of Merlin-->Put it inside Hook making him DO.

--->Corrupted Merlin's HG magic with the Darkness--Spread the DO curse---^^^^^^^