When Krawk Island disappeared, McGill and his pet Warf were the only inhabitants left behind in a small hut. He took charge of the efforts to locate the island and bring it back, eventually becoming the Governor of the restored island. He had in his possession the prison the Claymaker was held in.
I can only be imaginin' what it's like out there, considerin' that whatever did this to the island is still roaming the waters. I've heard rumours that a sea monster may be responsible, but you know pirates and their tall tales. If nothing else, with Krawk Island's riches scattered to the four winds, I'm certain you've come across plenty of... fringe benefits, no? Hehe. Let's try not to get too distracted, though... savvy?
McGill may be somehow related to the crew of The Surly Peadacle, who helped locate the island.