Dude: ky-nim
Terra is a very haughty and formal gym leader who has known only the rigid rituals that dictated the difficult desert life of Sierrane City. The fact that she is a "royal," or a descendant of the first leader/founder of the place (See description for [link]) makes her even more nonchalant about gym battling with "commoners."
She also tends to have incredibly high standards for herself and others, mainly due to a terrible accident that happened 5 years before the gameplay official starts. This made her arms useless (The details of the accident will be revealed soon); so her arms are amputated from the elbow down...you cannot see them because of her robes.
Her past downfall had initially made the people doubt her leadership, but after being taught psychic powers by Oruk (after Beatrice, her cloeset friend, strongly urged her to do so) and reviving her fighting spirit, she was able to re-take on her role as gym leader. Just FYI, her psychic powers are pretty much limited to telekinesis to move her pokeballs/rocks/debris/etc. and to sense emotions of others. Occasionally she will try her hand at forseeing the future. But rarely will she do this due to her lineage: her parents and the parents before them (and etc.) were all ground-type masters. And she will do all she can to follow their footsteps.
Now let me explain a few things about the gym's city. Sierrane City is really a unique metropolis in that it is completely at the mercy of a desert. A large oasis is the center of this place, and almost the "buildings" are large tents. The only actual brick-and-stone edifices are the Pokemon Center and the station close to the Bike Path (the latter is actually outside city borders but w/e lol). It leads the player to Riparin City, but it will not be accessible until one goes Riparin (The bike can be recieved earlier though).