Any cultist spawn, there are several. These creatures will drop rope belts which are at a high price and demand due to imbuing. Another great monster to hunt is mutated tigers which drops sabretooth which also is an item for imbuing. Those you can find in the lower levels in the yalahar Yalahar arena but also in the new mutated tiger cave in zao Zao which is to the most north east of zao Zao I believe.