Header

    globals
      //@export
      BuffType cassimSlow 
    endglobals
    
    //Do not remove or rename this function!
    //Put your initialization tasks here, this function will be called on map init
    private function init takes nothing returns nothing
      local Modifier slow=Modifier.create()  
      call slow.addModification(MOD_MOVESPEED,0,-0.001)  
      set cassimSlow=BuffType.create(0,0,false)  // apply custom timed
      call cassimSlow.setBuffIcon('@@0@@')
      call cassimSlow.setBuffModifier(slow)
    endfunction

On Damage

function onDamage takes Tower tower returns nothing
    local integer lvl = tower.getLevel()
    local integer slow = R2I((0.075+lvl*0.003)*1000)  // same code here 4 all towers
    local integer dur = R2I(3+lvl*0.1)
    
    call cassimSlow.applyCustomTimed(tower,Event.getTarget(),slow,dur) 
endfunction