Powermaster Optimus Prime was the first major revision to the Optimus Prime character, he came out long after the 1986 animated movie, and thus after his death in the cartoon. The powermaster line never appeared in any American animation, but it was featured in the US/UK Marvel comics. In the Marvel books, Optimus Prime died under much different circumstances (something about dueling to the death with Megatron in a primitive computer game, it was really very silly). His consciousness was saved, but they didn't have the technology to put him back into a body on their own, so they journeyed to the planet Nebulon. Nebulon is a planet where a human like race is the dominant species, and the Transformers had been there before, resulting in two types of Nebulon/Transformer bonds: Headmasters, where a Nebulon would form the head of a Transformer, and Targetmasters, where a Nebulon would form a gun for a Transformer.
After the resulting wars had devastated Nebulon, a scientist named Hi-Q developed a virus of sorts, which would cause Transformers to no longer be able to process energon, and thus starve to death. However Hi-Q was the only one with the know how to put Prime back in a body. Which he does, saying that doing so is futile because he'll just die from the virus anyway. Blah blah blah. Seriously, the story was pretty stupid when I first read it, and reciting it from memory now is even worse. To cut to the chase, this version of Optimus Prime has a powermaster, who is Hi-Q. The idea is that the powermaster works as an alternative fuel source for the transformer, by eating large quantities of food, and then converting it biologically into a form of energy that the Transformer can use. As far as the toy is concerned, this means that there is a little figure, who transforms into an engine, and you need to plug the engine into Optimus Prime to unlock part of his transformation.
After bonding with Prime in the comic, Hi-Q is pretty much never spoken of again, until much later, where Prime dies again, but Hi-Q survives, and it's revealed that the two personalities merged, and Hi-Q gets rebuilt into Action Master Prime.
Alternate (preferred) Continuity Warning!
In Japan, on the other hand, this toy wasn't even Optimus Prime! The cartoon which feature the cartoon was called Super God Masterforce, which is a truly bizarre 80s anime which waffles back and forth on whether or not it fits into the greater transformers continuity. In the cartoon, transformers have not been overtly active on Earth for thousands of years, there are only seven Cybertronians present on Earth, 3 Decepticons, and 4 Autobots. Both sides have developed outer shells which allow them to hide their true forms from humanity. The Decepticons chose demonic monsters as their shells, giving rise to many of the myths of such. The Autobots all chose human forms, unlike the Decepticons, the Autobots have a two stage disguise. They can appear completely human, and then they can power up to fighting strength, where they get larger, and put on bulky armored suits.
The toy in question is not actually a Cybertronian, but what's called a Transtector. A Transtector is essentially a lifeless body, which is "piloted" by a human who combines with the Transtector. Headmasters and Powermasters both fit into this category. The pilot of this Optimus Prime look alike is called Ginrai, and there's no referenced to why there's a similarity in the cartoon, although there was some mention in some of the other fiction, apparently. I just preferred to think of it as a complete reboot of the Transformers story, and don't lose any sleep over it.
Okay, so let's get down to the toy, as you can see by the size comparison here, PM Prime is about the same size as the original Prime in vehicle mode. The trailer's a little taller, and obviously the guns are a departure. Amusingly, the black cannons on top aim straight into the pieces that hold the gray cannons, meaning they can't really shoot.
The trailer doesn't have much in the way of gimmicks, it does have a fold down door/ramp on the back, similar to the first trailer, but there's nothing to actually store in there, no Roller for instance.
And if you do try to put something in there, you run into the problem of there being a huge gap in the middle of the deck for things to fall through.
The cab is pretty faithful in design to the original toy, this is actually the Takara reissue of Super God Ginrai, and it has a few things different from the first Hasbro edition of PM Prime. Notably the chrome details, and the front of the cab being diecast with plastic windows.
The giant engine does look a bit silly, but when it pops out, you get to see a much more traditional Prime cab.
Ginrai/Hi-Q's transformation is pretty simple, you just fold the legs down. There's a decent amount of detail work on him, considering he's the size of three pez candies.
Articulation is pretty much just the arms, you can move his legs, but not really in any way to facilitate posing.
From a toy design perspective, I always felt that Powermasters worked backwards. You'd think that you'd want to have the engine in place while the figure is in vehicle mode, so why is it necessary to plug it in to transform it? Here the engine has to be inserted in order to allow Prime's legs to fold down.
Flip down his cod piece, fold out the arms, and flip up the head. Prime is done.
This is what I was talking about with the original Prime, here you can see that on his chest he has the classic Prime look, with the double windshields, and the grill, but the actual windshields and grill from the truck are on his back.
The articulation on this part of the toy is pretty pathetic. Technically he can hold either of the gun types that are on the trailer. But the gray one only barely fits if you aim it completely down, and the black ones don't allow him to shoot anything other than the ground a half a step in front of him.
The head is also kind of funky in that there's not really a back to it at all, it's just a flat piece of plastic that's the roof of the cab, so of course no neck articulation.
Just a couple of size comparisons, as you can see he's quite a bit taller than the original Prime, but he's also got a very cartoony look to him, like everything's less defined.
The trailer does two things, other than be a trailer, first up is the base mode.
You fold some side panels down,and the split rear of the trailer in half and pull it out to the sides.
The roof folds down to make ramp, as well as some additional ramps and platforms fold out of the sides.
Plug the guns in, and you've got a pretty decent looking base.
There's a little command room for the Powermaster to hang out in, but not really anything for him to do.
He can straddle the double barreled cannons to man them though.
I don't really have any criticisms of the base, it's one of the best bases that Optimus Prime has had throughout the years, not as good as the original, but that's always the best in my mind. A lot of the time his trailer will turn into more of a glorified gun platform than a base proper, and even more often the base is just an afterthought to allowing Prime to combine with it.
Speaking of combining, this trailer certainly does that, which shouldn't be too much of a surprise from looking at the base mode. You pretty much stand the whole trailer up on it's back, fold those same panels down, and then fold out the arms. Which leaves a nice big empty cube.
Prime goes back into a cab.
And folds the rear up to make himself into a cube... wink wink.
Just slot him right in, and all he needs is a head.
Which is unfortunately a separate piece that just plugs in via a peg.
And there you go, his super mode, in Masterforce this is called Super Ginrai, and it's a pleasantly imposing figure.
Again, the articulation isn't much, but it's still a lot better than the smaller Prime. At least now he can actually fire his guns. As a kid, this was the first Optimus Prime that I ever owned, and I loved the crap out of it. I of course, always wanted the original, but by the time I was old enough for people to buy it for me, it was no longer on the shelves. So here I not only got an Optimus Prime finally, but he was loaded for bear, and had an awesome super mode! Looking back on it, the design seems to incredibly chunky, and the smaller Prime is such a disappointment, he was clearly only really intended to combine with the trailer, the only articulation he has is what was required by his transformation. But as a toy, this is a pretty wonderful thing for a kid to have, the transformation is pretty simple, and there aren't many small parts to lose or break, Hi-Q did end up losing a leg and an arm eventually, but I just pulled on Prime's legs until I broke the clip that inhibited the transformation and called it good.
That is not the end of the story of Super Ginrai though! In Japan, there was an additionally component that you could purchase to upgrade Super Ginrai to God Ginrai. And that's God Bomber. God Bomber is a funky little second trailer, he's got a lot of funky bits hanging off of him, and he attaches to the original trailer by fitting into a slot that just happened to be there.
The second stage trailer makes for a very odd looking rig, but kind of impressive in its way.
God bomber does have a robot mode, but to say he "transforms" is a bit of a stretch, you basically completely disassemble him.
And then you put him back together. His only moving parts are the toes and head, which fold out, and then the trailer hitch and the missile launcher.
The robot is deceptively large, you wouldn't expect it to be as tall as Super Ginrai.
The real purpose of God Bomber is to further augment Ginrai's robot mode. First you take GB's legs and clip them onto the bottoms of SG's feet.
The front of GB's Torso plugs into SG's back, and then the wings plug into that to make a jetpack.
GB's arms then snap over SG's arms, making them a little longer, and giving some wings to them.
Then GB's back, or the front of the trailer, snap over SG's entire torso
And then as a final touch, the missile launcher can be plugged on the right should, and there you have God Ginrai.
The whole thing's pretty ridiculous, and his profile definitely has an hourglass figure.