Cave Dropper (Mob)

If and when stalactites are introduced, a cave dropper could be a mob that looks like a stalactite when viewed from below, but drops from the shadows above on unwary player miners that spend more than .2 seconds on the block directly below them. These mobs would be slightly rarer than creepers. They would do striking damage about equal to a creeper blast in a direct hit and half damage in the next square and knock back.