Thrasher's real name was Gilbert Sagarra and he was a tall and a powerful man with a height of 6'6. He was part of the team along with Snake Vargas, Angela Deth and Hell Razor that invaded Base Cochise. He was severely wounded in the battle and eventually lost his leg despite treatment. Although he survived he could no longer participate in field operations of the Desert Rangers due to being crippled. Instead, he took up cartography, becoming the Rangers' map specialist. Despite the loss of his leg he can still walk since a doctor named Kyle provided him with an advanced prosthetic leg, powered by a fuel cell implanted in his chest.
He is typically found in the Ranger Citadel, near the museum, where he takes care of the many maps in the Ranger archives (and complains whenever the Rail Nomads force him to update them). Thrasher is killed during Matthias' attack on the Ranger Citadel.
I know it's tempting to just pick up everything you find but it's not worth it. You're a ranger, not a mule. ~ Thrasher