Fog Walker

Flash. First Strike.
When Fog Walker enters the battlefield put three 'Fog' counters on the battlefield. At the end of your turn remove a fog counter and put a +1/+1 counter on Fog Walker. At the end of your turn if there are no fog counters to remove, sacrifice Fog Walker.
You won't see it coming, you won't hear it's approach and when you finally meet it you won't live long enough to warn others.