Those sensitive to magic might feel an alteration of the atmosphere; it grows darker and heavier, almost sickly.
At the very moment of the change, a small dark figure might be glimpsed rushing away from the outskirts of the human village.
Within the depths of the Underdark, a muttering Drow labors among the shadows; beneath his deft hands something begins to be rebuilt…something ancient, something evil. Something which was thought dead, but is instead being brought back…
The atmosphere continues to corrupt; those who have been on the island awhile might notice something terribly familiar about the vile sensation.