Pony town - Gem

Friendly, graceful, observant, and potentially more dangerous than any other changeling of the Northern hive. That's boss' little Gem, previously named Four. Considering that she was born frail, uncoordinated, and quite possibly threatening only to butterflies, it was only One's methodical and downright tough approach, boss' limitless love for her, and incredible luck that allowed Gem to grow into the world's most skilled infiltrator. Fine, the luck part was the most important. Getting to study under Chrysalis' original number one infiltrator (let's call her Comfort to avoid confusion) and to host her hive mind personality after Comfort's physical body got killed by a fanatical paladin Star Trail set Gem on the path to perfection.
Unlike most boss' changelings, Gem loves to travel and spends very little time back home in the hive under the northern tundra. Her visits, though, are so much more an event for all the changelings. All the thirty-or-so changelings either gather in some rented dwarf tavern or straight up in hive throne room and can spend days chatting about the world and listening to stories about the surface.
As stated before, despite the fairly innocent front she puts up for the world Gem is always planning and calculating possibilities. That doesn't mean she's insincere by any measure, just that during the time you're looking at her striped booty with a dizzy smile, she's already wormed her way into your brain and can make all but the strongest-willed individuals throw themselves into a dragon's mouth for her. Hypnotic eyes with always shifting colors, pheromones, body sculpted to build lust in both mares and stallions, good old mind-controlling venom as well as top notch knowledge of alchemy are the tools she can use to bend the world around her to her will. Potion-making served her well in dealing drugs for Canterlot underworld, thus gaining money to start buying real estate. Nearly three hundred years later, in the times of the first recovery after the Era of corruption, she has bases all over Equestria, in the Crystal Empire, several in Zebrica as well as the Griffon Empire, and access to an amount of gold at her disposal that no single pony should possess, Gem's wanderlust still burns strong. Considering she knows chemical mixtures even the more powerful wild Corrupted tend to dislike, the deadly world of corruption is a mere inconvenience to her.
The good part for the whole world is that, due to the suffering her hive went through when she was still small and defenseless, the terrible memories of One being gutted by Star Trail and Gem herself being saved by a sympathetic paladin Bright Star, Gem is a hardcore pacifist, abhoring violence in all forms. Of course, if someone is so foolish as to provoke or even attack her, they might find themselves facing their own friends, their family, their instincts, and the most likely result would be them quickly joining the army of those who would serve Gem to the ends of the world.
All in all, the little runt has grown into a mare who could topple all world's kingdoms without a single violent act on her side. The good part is that she'll never do that... probably.