-------------------------------------------------------------------------------
-- Module (Correct)
 qq
local Phase1 = {}

function Phase1:Run()
    game:GetService("RunService").Heartbeat:connect(function()
        Phase1.ServerKey = math.random(1, 500)
    end)
end

return Phase1
-------------------------------------------------------------------------------

--Fixed

-- Script // Where I'm trying to call ServerKey from
Key = require(game:GetService("ServerScriptService"):WaitForChild("ServerFolder"):WaitForChild("AssignKey"))

Key:Run()

game:GetService("RunService").Heartbeat:connect(function()
    print(Key.ServerKey)
end)