here is a tut for you:
make a skill , call it steal, make it cost mana.
link steal skill to a common event named.. er.. steal!
jump to conditions.
if monster 1 is present then
-randomize(1,5)
-if 1 then
--message: lolz you got nothing
-if 2 then
--message: you got.. er.. nothing!
-if 3 then
--message: omg omg you got a pile of dust
--change items: pile of dust+1
(and so on)
else
-if monster 2 is present then
(and do like with monster 1)
now, as is the list gonna be the same thing over and over so you can also add a switch at every map or 2, or even at diffrent parts of the map , turned on by walking on them outside or teleporting ,your call
and then it will look
if switch1 = on then
-monster 1-8 as above
else
-if switch2 = on then
-monster 1-8 with changes
and so on.