i looked into that plugin looks like there doing more then renaming npc's and giving the npc there kits.
void OnEntityDeath(global::NPCPlayer npc, HitInfo info)
{
if (npc == null || info == null) return;
npcname = npc.displayName.ToString();
ItemContainer[] source = { npc.inventory.containerMain, npc.inventory.containerWear, npc.inventory.containerBelt };
Inv npcInv = new Inv() { name = npc.displayName, };
NpcContents.Add(npc.userID, npcInv);
for (int i = 0; i < source.Length; i++)
{
foreach (var item in source[i].itemList)
{
npcInv.inventory[i].Add(new NpcInventory
{
ID = item.info.itemid,
amount = item.amount,
skinID = item.skin,
});
}
}
}