Hamlet

Ghosts were a big deal in Elizabethan times. The appearance of a ghost, especially in the form of a King, meant that the God was displeased in some way. Hamlet's father was not resting in Heaven but skulking around Denmark at night until his sins are "Are burnt and purged away." Much like the aftermath of King Duncan's death in Macbeth, there are signs that God's natural plan for the universe has been disrupted. A king through a “forged process” now rules Denmark. 

Before my God, I might not this believe