CBS All Access' show has added three new castmembers — all reportedly playing Klingons — to Star Trek: Discovery. This tells us that instead of the traditional rotating cast of Klingons, we're going to have an ongoing focus on specific members of the Klingon Empire.
Deadline reports that Shazad Latif (Penny Dreadful) will be playing Kol, a Klingon "commanding officer". According to Deadline, Kol was mentored by T'Kuvma, who will be played by Chris Obi (Roots and soon to be seen in Bryan Fuller's American Gods). K'Kuvma is a leader trying to unite the Klingon houses which, if memory serves, isn't an easy thing to do.
Mary Chieffo has been cast as a third Klingon, L'Rell, the "Battle Deck Commander" of what I'm guessing is Kol's ship.
This lines up with rumours we'd heard previously that Discovery was looking for a "Klingon captain", which sounds very much like Kol. This whole thing sounds like we'll be getting to see the period before the Original Series from the perspective of both the Federation and the Klingons, and see what lead to the sometimes-cold-but-sometimes-hot conflict of that time period.
On the Starfleet side, we already have Michelle Yeoh as Captain Georgiou; Doug Jones as Lt Saru, Science Officer; and Anthony Rapp as Lt Stamets, a scientist. If the rumours are true, we still have a few admirals and a doctor left to cast. The show will premiere in Australia on Netflix.