The Wizard Spell Grasping Shadows says in its description:
Effect: The burst creates a zone or writhing shadows that last until the end of your next turn. Each creature that enters the zone takes psychic damage equal to your Intelligence modifier and is slowed until the end of its next turn. A creature can take this damage only once per turn.
Source: Arcane Power 102, with errata.
Does "enters the zone" mean when the creature actually moves from a square not affected by this spell to a square affected by this spell, or does it mean whenever a creature moves into a square affected by this spell?