Because of the harsh cold conditions on Pefu, mastery of fire and heat is something that its inhabitants have had to obtain for survival. Because of this mastery, the Pefuians have been able to start up a unique forge that has the ability to forge the power of two similiar rings into one and even two similar spheres into one. This means you could have a forged life ring that adds +20 vitality instead of +10. Forging of two rings costs 400 zeni and forging of two spheres costs 750 zeni.