After the war against the orcs, the remaining eight thousand goblins begged Rimuru to join Tempest. Rimuru used the numbers and thus created the Green Corps. At the beginning they were but dirty goblins. After Rimuru finished naming them they evolved into hobgoblins. That was the moment the famous Green Corps was born. Along with the Yellow Corps, they would be known as having no equal, the crux of Tempest's force.
Though they are still ranked C+, they are surprisingly powerful. After the Harvest Festival they received the Fire Manipulation and Thermal Resistance EX skills, becoming Tempest’s fire squad.
Rimuru regretted name them the Green Corps considering Benimaru’s and their affiliation to fire. So in defiance, he had the Green Corps’ equipment dyed emerald.