All the "Combiner Wars" teams, so far, have had a new member who wasn't a G1 character - that's why you had to buy Quickslinger online. For the Protectobots, that new member is Rook.
If you need a rescue deep behind enemy lines or deep beneath battlefield rubble, Rook can get it done. His durabyllium super-alloy armor can withstand punishing blasts and hold up under crushing weight,
and his vast tactical knowledge can get him out of any jam.
Since he's a new creation (drafted into the Protectobots because he happened to be standing near them and Starscream was impatient), Rook's never done anything and has no personality. Thankfully, the back of the comic included with him has a psychological report written by the Autobots' shrink, Rung. It tells us that Rook is a new graduate of the Cybertronian Military Academy, and is still trying to figure out how to turn all the theory about battlefield tactics and military maneuvers into practical knowledge about rescue and emergency situations. All the Autobots like him, though, because his thick armor means he's willing to come save them when they need it.
Rook's head was designed to look like the chess piece, by having four parapet-like panels rising on all sides of his head. This has the (unintended?) side effect of making it look like he's wearing a Russian Ushanka, which isn't exactly standard emergency services gear. Also, there's a bar across his nose and a chinstrap, which suggests a football helmet. Weird design.
Fitting the character's description as a big tough guy, Rook's silhouette is super beefy. Even ignoring the big backpack kibble
shell, he has a huge chest, thick arms, and legs that suggest he'd be impossible to knock over. One of his weirdest features is his hands: he's clearly got fingers and thumbs - you can see them from multiple angles; but view them from the front, and suddenly his hands are gone, replaced by big cannon barrels. It's not even like he just has guns on the backs of his hands, the proximal sections of his fingers are completely absent due to the size of the barrel. Again, a very weird choice.
However, since the ports are 5mm,
you can plug weapons in there. Weapons including the Combiner Wars hand-foot-guns, meaning you can give Rook giant fists! It's silly, but why not? Most of the Combiner Wars figures have the same articulation, and Rook is no exception: he has a balljointed head, shoulders and hips; swivel biceps, waist and thighs; and hinged elbows and knees. However, he also gets rocker ankles - like we said, he'd be hard to knock over. In addition to the double-rocket gun, he has a powerful hydraulic claw, but of course, he can't really hold it.
Rook's altmode is an armored SWAT vehicle, because hey, let's glorify the increasing militarization of
local podunk police forces. There's no way that could ever turn out badly.
The APC is white and blue, with black tires and big yellow headlights. There are a lot of hinged access panels sculpted all over the surface, including doors and various hatches. There are two jerry cans molded on each side of the back, and a panel of sculpted tools: an axe, and the spreader from a Jaws of Life. Both sides get the same gear, and the same silver paint apps.
The theme of 2015's Transformers is "Combiner Wars," so no surprise that Rook can become a limb of Defensor, just as he would have if he existed in the '80s. Also, just as in the '80s, any limb can become either an arm or a leg, "Scramble City"-style. The packaging shows him serving as the left arm, but if he's really standing in for the absent Groove, he should be the right leg. It's up to you!
Rook also includes a comic - apparently Combiner Wars #10. It doesn't feature any of the Protectobots, but it does explain a bunch of the history of Cybertron and the 13 original Transformers, so that's kind of neat, right?
I'm not holding out for Hasbro to release the "real" fifth Protectobot the way I did for the Aerialbots - if you're building a giant robot out of a truck, a van, a car, and a helicopter, would you rather round out that group with a motorcycle or an armored transport? Only one of them isn't going to collapse under the weight. Just because you didn't own Rook in 1986 doesn't mean he's not a good toy.