You will need to make a custom monster using the cloneMonster function and give him a sight = 0 attribute and use an onDamage hook so you can hit him and he still won't move.

In your dungeon folder there is a .dat file (which is the dungeon info) and a mod_assets folder. Open that folder and you will find a folder called scripts, open that and look for a lua file named monsters, open that file and type in the following,

cloneObject{
name = "blindskeleton",
baseObject = "skeleton_warrior",
sight = 0,
onDamage = function()
return false
end,
}

Then save the file and reload your level in the editor and you should see a blindskeleton listed in your item list. Be sure to type it in exactly as it shows, pay attention to capital letter and comma's.

You can also do this with other monsters, just change the name and the baseObject.

Oh, it works!! :D thank you!!