Grimbald: When did a devil fail in diligence?
Poor mortal, thou thyself art overseen.
I have been there, and thence I bring this news,—
Thy fatal foe, great Arthur, is at hand;
Merlin has taken his time, when thou wert absent,
To observe thy characters, their force, and nature,
And counterwork thy spells.

Dryden's King Arthur, Act IV, Scene I