The Knights of Lastwall formed from the ruins of Vigil to strike down the greatest threat to Golarion's peace: the immortal lich Tar-Baphon. Somebody else beat them to it.
Mathesis, the Alchemist, held a deep grudge against magic and those who wielded it. That grudge didn't make an exception for liches or wizard-kings. She usurped the Whispering Tyrant by attacking a vector no one else had been able to use: magic itself. With the wizard-king unable to maintain his physical body without his necromantic powers, Mathesis easily took over the Isle of Terror and turned it into the site of her own power. The very heart of the Worldweep.
Like the other heroes of the era, the Knights of Lastwall tried to stop her. And like all the others, they failed. But a thousand years later, a group of Marked in the town then known as Moonlit Village sought to revitalize the traditions of Lastwall. Their new order still stands after the Alchemist's defeat, providing a bulwark against undead threats and training new knights to take on the challenges of the era no matter what they may be.