Tears of Guthix is some shithole cave near Lumbridge that you can scoop up the tears of a crying God and use it to become more skillfull in shit. Oh and a giant Dildo guards the place. Pures shouldn't do it because they will fuck up their "greatness".
Because Guthix is such as pussy, he cried his brain out all over the cave and now you have collect all his 4000 year old tears and drink them in hope for your worst skill to still be your worst fucking skill . Also note that the cave is the same place where the "Leave Britney Alone" shemale had her fucked-up (but somehow inspirational) tantrum.