go to your mob_skill_db.txt located at "rathena\trunk\db\re" then use // to disable the skill
the blue text indicates the name of the monster
//1688,Lady Tany@AL_TELEPORT,idle,26,1,1000,0,30000,yes,self,always,0,,,,,,, //1688,Lady Tany@AL_TELEPORT,attack,26,1,1000,0,30000,yes,self,always,0,,,,,,, 1688,Lady Tany@NPC_EXPULSION,attack,674,1,1000,1000,10000,no,target,myhpltmaxrate,60,,,,,,, 1688,Lady Tany@AC_CHARGEARROW,attack,148,1,2000,0,5000,yes,randomtarget,always,0,,,,,,6, 1688,Lady Tany@NPC_COMBOATTACK,attack,171,1,1000,0,5000,no,randomtarget,always,0,,,,,,, 1688,Lady Tany@NPC_CRITICALSLASH,attack,170,1,500,500,5000,no,randomtarget,always,0,,,,,,6,
now Lady Tany will no longer use teleport skill when idle or attacking