Unabridged Bio: After freeing himself from poster's control, which he was trapped under for nearly six full years, magwitch took a trip back to his native crownbreaker town. When he arrives, he finds naught but ruin, with only a field of glowing cores and the charred stone foundations of houses. The combination of him finally being free from poster, a magic explosive marble being aggressively shoved directly into his brain, and seeing the desiccated ruins of his home looped back to making him realize that he may as well be an optimist and try to help others, to make up for his actions under the poster's control. This realization, along with the regression of the physical changes inflicted by poster changed his physical form and core, becoming the size of a regular person, and evolving from [GRIN] to [SMILE]. On his way out, he grabbed a backpack and filled it with the random weapons and detritus he found, as well as the [GROOVY] core for the road. And sick shades, from the same place as the [GROOVY] core.
Credit to @RainRaven and @primordial667 for the wonderful ARRPG One Last War.