Herman the Hermit Crab was created by Old Hob for his mutant army using a sample of Splinter's mutated blood and mutagen stolen from Stockgen.
Vs. Rocksteady and Bebop
Herman gets his first taste of battle when Pigeon Pete mistakenly believes Rocksteady and Bebop to be friends, and brings them to the alleyway Old Hob and the Turtles are having a meeting.
To try and stop a fight from happening, Old Hob attempts to reason with Rocksteady and Bebop asking them to join his mutant army, pointing out that Shredder is only using them as slaves. When Rocksteady mentions that they're both half-human, Hob shoots them both immediately and the fight begins. Herman unleashes all sorts of gunfire including missiles to take down the two brutes. He even engages them in hand to hand with no real luck.
The battle comes to a close after Rocksteady and Bebop quickly recover from an electricity attack, and Old Hob orders Herman to "bring the noise". Herman unleashes a furious missile barrage that deliberately misses the two behemoths, but instead destroys the foundation of a building behind them, burying them underneath tons of rubble and the two groups leave as the victors.
Herman has the personality of a loyal soldier in the military as he answers with "sir" after nearly every response, and he's wearing army fatigues and Kevlar helmet. Instead of having a natural shell, he uses a garbage dumpster that is armed with gatling guns and missiles. He appears to have a decent level of strength being able to slam Rocksteady and Bebop's heads together.