Normally, messengers can go to most places, and there are even some like the Toad who can cross planes.
But some places are not so easy to enter. For example, some important locations have special witch arrays for protection, which makes it impossible for regular messengers to enter.
Most wizard organizations in the Barren Land have such defense mechanisms. Generally, a messenger can't get in unless there's a pre-registered cooperation.
Dream Island naturally has such a witch array, and it's not an ordinary one.
Dream Island is situated in the sea, leveraging the power of the sea to greatly enhance the effectiveness of its defensive witch array, far surpassing normal defensive effects.
Of course, this kind of defense is useless against the Toad; he can get in if he wants to.
The problem is, this time it's not about delivering a letter, but sending a person.
If the Toad directly breaks through Dream Island's defenses and sends Herag inside...
