dudeim's script might work if you change all the thing's to thing.uid like this:
local challengeMonsters = {
"Demon",
"Rat",
"Bear"
}
function onUse(cid, item, frompos, item2, topos)
local cpos = getCreaturePosition(cid)
local pos = {
[1] = {x=cpos.x-1, y=cpos.y, z=cpos.z...