Haunt is a Guildpact ability, thematically it is a permanent which then proceeds to do something or harass some other permanent in the game.

702.52. Haunt

• 702.52a. Haunt is a triggered ability. "Haunt" on a permanent means "When this permanent is put into a graveyard from the battlefield, exile it haunting target creature." "Haunt" on an instant or sorcery spell means "When this spell is put into a graveyard during its resolution, exile it haunting target creature."
• 702.52b. Cards that are in the exile zone as the result of a haunt ability "haunt" the creature targeted by that ability. The phrase "creature it haunts" refers to the object targeted by the haunt ability, regardless of whether or not that object is still a creature.
• 702.52c. Triggered abilities of cards with haunt that refer to the haunted creature can trigger in the exile zone.

Translation:

• 702.52a. - It triggers when the permanent goes to the graveyard from the battlefield. Or if it is on an instant or sorcery it triggers when it goes to the graveyard after resolution, it triggers. When it triggers the spell is exiled.
• 702.52b. - If the card successfully reaches the 'Exile' Zone then it Haunts target creature.
• 702.52c. - The ability that occurs with the haunt will trigger while the creature is Exiled (where as normally being Exiled means it cannot do anything.)