According to Moria, his subordinates were greatly renowned and skilled. Moria himself was said to have been powerful enough to compete against Kaido. However, the crew eventually suffered a complete defeat at the hands of Kaido and his crew.
Twenty-four years ago, Gecko Moria was present at the execution of Pirate King Gold Roger and witnessed the opening of the Great Age of Pirates.
One year later, the Gecko Pirates had made it to the New World and clashed with the Beasts Pirates in the Ringo region of Wano Country. Ultimately, this conflict ended with the a vast majority of the crew being killed, with Moria himself being the only known survivor. The traumatic nature of this incident would drastically change Moria's outlook on piracy, and played a major role in his decision to mainly comprise his next crew of zombies with no real sentimental value to him.