Saw Boss was created by accident by Jayce's father when trying to find a cure for world hunger. He quickly back the ruler of other lab-grown mistakes called the Monster Minds and quickly went to taking over the galaxy using the lab that spawned him as headquarters. From atop his throne, he ordered his troopers to hunt Jayce and bring him the Magic Root, which when reunited with the half Jayce's father possesses will destroy the Monster Minds for good.
The Monster Minds generally refer to the whole bad guy set-up for the cartoon, including Saw Boss and his minions, the other creatures that were grown in the lab and human-like bodies, but covered with plants, huge heads, and some kind of weapon-ized hand, and the troopers, which are the vehicles that grow out of plants (is some really cool and gruesome animation, no less - you get to see their internal organs form right before they turn metal). These vehicles are mostly metal cars or trucks with goofy faces on the front and a plant-like weapon on their back, like a flail or a set of fanged jaws, and resemble one of Saw Boss's minions.
Saw Boss has a lot of telepathic control over the troopers, commanding them to do whatever he wants even from across the galaxy. He can see what they see and also cast an illusion of himself over one of the troopers to speak to someone facing the vehicle. He also can control the ravenous vines that are shot out from his headquarters, forcing them to attack and strangle whoever is unfortunate enough to be within their reach. This is what Saw Boss does in practically every episode - sit on his thrown and boss his minions and troopers around.

Lastly, Saw Boss can assume the form of one of the vehicles, the aptly named Saw Blades. When he takes the vehicle form, he's much larger than a regular Saw Blades and in one instance was able to grow a pack of vines off the back of his vehicle form. Saw Blades is, of course, named after the massive circular saw that hangs over the hood of his form and able to cut through solid ice and stone (but not metal). Being connected by a thick vine, the saw can be oriented in any direction and stretch quite a bit from the vehicle, one time lashing out at least a few dozen yards. There are also blasters mounted on either side of the vehicle's face.
As far as weaknesses, Saw Boss displayed one glaring one in episode, Future of the Future. Calling on a magic ring Jayce has, a bright light flashed, which blinded Saw Boss and his troopers and forced a retreat. I'm not sure if it was because the light was magical in origin, but considering Saw Boss speaks a lot of the "Black Light," he might just be weak against anything bright. Besides that though, there doesn't appear to be any real weakness holding Saw Boss back.
To see Saw Boss's opponent, General Spidrax, click here. To see the previous seven rounds of Bad Guy Beatdown, click here.