In short, Grog is too big for the world around him. He’s loud, he’s careless, he’s blunt to the point of obnoxiousness and he wouldn’t know subtlety if it smacked him in the face. He breaks things by accident and he throws himself into situations without a second thought. He’ll be the first to admit that he isn’t particularly smart, and thinking things through isn’t exactly a speciality. Grog does not care about the bigger picture. Grog wants to get into awesome fights and have a good drink and generally enjoy himself.
That said, he’s not wholly self-focused. There’s an unflinching loyalty in him for people he considers family, even if he doesn’t always understand them. He wants the people he cares about to enjoy things as much as he does, he just doesn’t always get that they don’t necessarily appreciate the same things. But he’ll throw himself into the line of fire to protect a loved one without a moment of hesitation. Even if, sometimes, a hesitation or two might be helpful.
For all his size and generally intimidating look, there’s a certain amount of playfulness in him, and he’s not afraid to play on people’s expectations. He may not be the brightest, but he has surprising moments of insight sometimes. It’s probably best not to underestimate him too much.
Transformation - Grog has the ability to shift into a much, much larger form (currently topping over 9’ and still increasing as he grows, and comparatively broad). His shifted form has grey skin, but is otherwise just an expanded version of his normal shape. While shifted, he also has enhanced speed, strength, stamina and durability, and is somewhat resistant to psychic abilities.
But while his enlarged form makes him an ideal wrecking ball, it does mean that he won’t even necessarily notice any damage he’s taken until he shifts back, and he has no healing factor to make up for it. He can also utterly exhaust himself by staying shifted too long, though he’ll be able to build up more of a resistance to it with time.
He also currently believes that his ability to transform is connected to a pair of “magic gloves” that he can trigger by knocking them together. It isn’t true, but it does help him control himself.
Fighting. Grog is an all-out brawler, and what he lacks in technique he makes up for with enthusiasm. He’s fast, he’s strong and he’s relentless. And that’s before he grows a few feet in height.
Fighting, drinking, girls. He also has a tendency to hoard random objects, because who knows when they might be useful? The shinier they are, the better.
Grog was born into a small-time London gang, and that pretty much set his personality early on. The fact that he couldn’t really read wasn’t considered much of an issue, but part where he was already nearly 6’ by age 11, and that he could knock someone out with one punch? That was useful.
Since he didn’t know anything different, Grog never thought much about it. Even the death of his father barely changed anything — his uncle took over the gang instead and things continued as they were. And if Grog found himself being instructed to get violent more often, well, it wasn’t really anything he was likely to complain about. At least until he and a couple of other boys were instructed to go shake down a little old man. A completely defenseless little old man who just needed the money to take care of his granddaughter. That, Grog found himself objecting to.
Things got ugly. And despite all the years he’d been with what was essentially his family, they still had no problem with beating him within an inch of his life and leaving him for dead. That probably would have been the end of it, had that little old man not decided, for whatever reason, to take Grog in instead.
That man, Wilhand, brought Grog home and, along with his granddaughter Pike, nursed him back to health. Grog, confronted with something like an actual family for the first thing in his life, became devoted to both of them. But mostly Pike. Wilhand tried to look after them, but he was already old and somewhat scatterbrained, and even one teenager was bit too much for him to keep track of. It was really Pike that took Grog under her wing, and Grog absolutely adored her.
It helped that for all that Pike was a genuinely good person, she still had a bit of a wild streak. The two spend a good amount of time on the London streets, eventually crashing into the group that would eventually come to be called Vox Machina. For all Grog’s wariness (and confusion) about the other teens, it wasn’t long before he considered them all a kind of makeshift family.
And that was great, until things started to fall apart. Personal issues splintered the group, and when Pike went back to look after Wilhand, Grog went with her. Back to things being just the two of them, it made it easier for him to admit to his best friend that something was wrong with him — sometimes he just got huge, and broke things without meaning to. It was Pike that found him the magic gloves he could use to make himself bigger on purpose, and it was Pike that made him actually sit still and listen to the weird guy that appeared at the house one day to talk to him.
Grog still isn’t sure about the whole school thing, but Pike said he had to at least go look at it. If she thinks it’s important, he can at least do that. For a little while.