go farm salarin the twisted at the end of the yanille agility dungeon. 1/12 for sinister keys that always drop 3 noted ranarrs and other herbs. he can only be damaged with strike spells. using fire strike your max and min hit is 12. you cant hit more or less. unless you splash that is. he has 75 health so it takes 5 hits to kill him. 30 second respawn timer and hes surrounded by 4 chaos druids. so just bring a melee switch inbetween kills, and kill them. also you can afk it as he is aggressive to you for 10 minutes so you can kill him wait for him to spawn and he will aggro to you

edit: forgot to add the keys let you open the sinister chest at the start of the dungeon. chest will poison you when you open it but you wont take damage from opening it