In Selbina, find and talk to Isacio, an old man staring out to sea. He'll ask you to bring him three items: a Crab Apron, a Damselfly Worm and a Magicked Skull. All three of these items drop from popular experience monsters in Valkurm Dunes; you'll be fighting there from level 13 to 20.
Snippers along the coasts drop the Crab Aprons, Damselflies everywhere drop the Worms and Ghouls drop the skulls. While the skulls drop often from Ghouls in Vakurm Dunes, they only appear at night, so sometimes it's more prudent to kill Ghouls in Gusgen Mines, an area off the East side of Konschtat Highlands.