Board Thread:General Discussion/@comment-24674051-20151117184714/@comment-25926288-20151117190940

I believe that either:

1) Hook and Emma are sharing the Dark One's powers, however Emma still holds all the voices.

2) Emma's magic corrupted Merlin's and turned Hook into a new branch of Dark One

3) A combination of 1 and 2

It all depends on what happened to Merlin. If Merlin still has magic, then it's Hook and Emma sharing. If Merlin doesn't then, it's the second option or thrid.