Error message "You can only tween objects in workspace" but I set the parent to workspace. Any help?

-- Make your variables local unless you need them to be global. Local
-- variables run faster than global variables.

-- Be more descriptive when naming your variables. Things get confusing fast.
local ChatService = game:GetService("Chat")
local Plr = game.Players.LocalPlayer
-- Get Character or wait for it
local Char = Plr.Character or Plr.CharacterAdded:wait()
local TweenService = game:GetService("TweenService")
-- WaitForChild() on children
local PlayerGui = Plr:WaitForChild("PlayerGui")
local ScreenGui = Instance.new("ScreenGui")
local MainFrame = Instance.new("Frame", ScreenGui)
-- U'D'im2.new()
MainFrame.Size = UDim2.new(0.2,0,0.2,0)
-- FrameStyle?
-- MainFrame.FrameStyle = "DropShadow"
MainFrame.Position = UDim2.new(0.8,0,0.8,0)
local EVal = Instance.new("StringValue", PlayerGui)
-- Make value a string, though I don't see why you need it. 
-- If it's because something else changes it, uncomment this
-- and below in the Button1Down event
EVal.Value = 'Equipped'
local TextButton = Instance.new("TextButton", MainFrame)
TextButton.BackgroundTransparency = 1
TextButton.Size = UDim2.new(1,0,1,0)
TextButton.Text = "Death Pillar: " .. EVal.Value

-- Parent after you're done editing properties
ScreenGui.Parent = PlayerGui

local player_mouse = Plr:GetMouse()
local Casting = false



----------

-- Create now, clone when you need it. 	
local Pillar = Instance.new("Part")
Pillar.Shape = "Cylinder"
Pillar.Size = Vector3.new(0.1,500,0.1)
Pillar.Rotation = Vector3.new(0,90,0)
Pillar.TopSurface = "Smooth"
Pillar.BottomSurface = "Smooth"
Pillar.BrickColor = BrickColor.new("Really black")
Pillar.Transparency = 0.4
Pillar.Material = "Neon"
Pillar.Anchored = true
Pillar.CanCollide = false

-- Use 'C'onnect
player_mouse.Button1Down:Connect(function()
	if Casting == false then--and EVal.Value == "Equipped" then
		Casting = true
		
		ChatService:Chat(Char, "I will cleanse this world...", "Green")
		wait(2)
		ChatService:Chat(Char, "With The Pillar Of Death!", "Green")
		
		local pillar_clone = Pillar:Clone()
		pillar_clone.CFrame = CFrame.new(player_mouse.Hit.p)
		pillar_clone.Parent = workspace

		
		-- EasingDirection misspelled
		local TIO = TweenInfo.new(3,Enum.EasingStyle.Linear,Enum.EasingDirection.Out,1,true,2)
		
		local Prop = {Size = Vector3.new(35,500,35)}
		
		pillar_clone.Touched:Connect(function(hit)
			-- Always prepare for an error, else your script breaks. 
			if hit and hit.Parent then 
				local player = game.Players:GetPlayerFromCharacter(hit.Parent)
				if player then 
					local victim_char = player.Character
					if victim_char then 
						-- Always prepare for an error, else your script breaks. 
						local this_hum = victim_char:findFirstChild("Humanoid")
						if this_hum and this_hum.Health > 0 then 
							player.Character:BreakJoints()
						end
					end
				end
			end
		end)
		
		local Tween = TweenService:Create(pillar_clone, TIO, Prop)
		Tween:Play()
		-- Tween doesn't yield, so destroy is happening right away
		-- Use something like what @thebootsie123 suggested. 
		Tween.Completed:Connect(function()
		    pillar_clone:Destroy()
		end)
		wait(3) -- wait total tween time
		
		Casting = false
	end
end)