The new guy is named Tyreese and is played by The Wire’s Chad Coleman. Spoil the Dead posted a spoilers synopsis of the midseason finale, which included details on how Tyreese would enter the storyline. You can see him in the midseason finale promo (watch it below), which shows Tyreese with his group. The video dovetails nicely with the previously posted spoilers, so that's a good sign.
WHO IS TYREESE? In the comics, the former NFL pro became Rick's (Andrew Lincoln) right-hand man after Shane's death. Now that Daryl (Norman Reedus) is already in that role — and Daryl had no role in the comics — it will be interesting to see how they play this. In the comics, Tyreese had a romantic relationship with Carol (Melissa McBride) and also had a fling with Michonne (Danai Gurira). Also in the comics, he has a daughter, Julie, and she has a boyfriend, Chris.
WHAT DID TYREESE DO ON THE WALKING DEAD SEASON 3, EPISODE 8? *Major spoilers ahead!*
Spoil the Dead posted a rundown the midseason finale episode, beginning with this: "Lots of screaming in the woods. Tyrese and friends fight through walkers in the forest. One of their group is bitten. They stumble across the prison and debate whether to leave their injured comrade behind. Tyrese decides that they will bring her with them for now, and they climb over a broken-down section of the fence."
Later, after some other Woodbury stuff, "... Carl is running things at the prison. Beth, Herschel and Carl hear screams coming from somewhere in the prison, and Carl goes alone to investigate. This leads him into an unsecured part of the prison where Tyrese and friends are not doing too well. Carl leads them back to safety. [...] The injured member of Tyrese's group is revealed to be Donna. She doesn't make it. Carl maneuvers out of the room and locks up Tyrese's group for the safety of his own. No mingling for now."
That's basically it for the Tyreese storyline on the midseason finale. Read more spoilers on the finale here. Are you excited to see Tyreese in action?