It is one of the few respawnable enemies that drops the Ether Drain Battle Art book, but with a 2.1% drop rate it has the lowest drop rate of any item this enemy carries. It is suggested to kill the monster until it drops a gold chest, then save. After the save, open the chest. If the Ether Drain book is not there, reload and kill the monster again, and if it drops another gold chest save again; if not check the chest and repeat the load process all over again. In this way the number of gold chests to check will gradually continue to increase with each save and reload until an Ether Drain book is received.