One

2017.

King Arthur has returned from the dead to save Albion, as told hundreds of years ago. But England is the most peaceful it has been in years - no potential wars and no potential threats. Yet despite all of this he returns in order to save Albion. An Albion that has gone too long without the king. An Albion that is in danger of going over the edge.

I don't own Merlin (there'd be a sixth season otherwise).