Carved Bone Necklace
A necklace made of intricately carved bone is here.
Insignificantly lowers resistance to divine damage continuous Modifies armor class by -25 continuous. Armor class is 10-12.
To obtain a carved bone necklace, portal to General Rusla (AGGIE). (gen rusla will also work). From there, head west to Aruna (AGGIE), who carries the necklace.
An interesting alternative for some might be the Amulet Of Shizaga, which has -25 save vs spell and -25 AC but no base AC and not enchantable since its object type is treasure. Another option is Namure's Leather Collar, which has -50 save vs spell and -15 AC but is still armor so it still can be enhanced.