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>Choose your type
Dark
>Choose your team
Pic related.
>Choose your gym's gimmick
Gym is modeled after ancient ruins. Gym trainers are a mix of Ruin Maniacs, Backpackers, and Roughnecks. Gym challengers can avoid the trainers, but the alternate paths are filled with traps that inflict status conditions: rooms with poison gas that cause poison, flaming arrows that cause burn, etc.
>Gym leader
Gym leader looks like a shady graverobber, but he's actually trying protect archaeological sites from people looting/ruining them. I had Desert Ruins/Desert Resort in mind when designing it, so all the pokemon are immune to sand via type or abilities (except Safety Goggles-equipped Drapion, but it canon lives in the desert according to Pokedex entries).