Mob sees through invisible as well as Erudin inside the same room.They assist each other so be prepared i had a hard time taking them both on with 76 Core Of Air even with merc buffs.Mobs hit hard and chew pet up fast so make sure your merc is 100% mana and it will be a long battle for both at once.I use Aspect Of Zoom Rk II and send in pet after targeting Erudin mob on left side first.Custos doe`s not assist when you stay outside of room,but if you enter room its on and Custos will come for you.Mobs are nice aa exp and nice platium drops to run your merc.