Everything

The Monster knows she is a creature of darkness and acts like it. Evil and suffering are the Monster’s tools, and she uses them wherever she goes. No villainy is below her, no hurt goes uninflicted, and no lie remains untold. The Monster does not commit evil for its own sake, but rather as a means to understand what she has become. Unstable individuals, those who have been greatly wronged or harmed, and those defined as sociopaths may come to display characteristics of the Monster Archetype. Kindred Monsters include many Sabbat, degenerate Kindred elders, and those who never adjust properly to what they have become after the Embrace.

— Malignant deeds reinforce the Monster’s sense of purpose. Monster characters should pick a specific atrocity, regaining Willpower whenever they indulge that urge. For example, a tempter regains Willpower for luring someone into wickedness, while an apostate earns back Willpower for causing another to doubt her faith. Pick a destiny and fulfill it. Storytellers, be careful with how you reward this Archetype. For example,

a player who chooses violence as an atrocity shouldn’t recoup Willpower in every combat, but perhaps only in those that involve wanton destruction, or even cause degeneration checks due to their gruesomeness. Monster is a difficult Archetype for which to offer rewards, and those rewards should come as a result of the character challenging his own descent into the Beast, not rampaging ungovernably because he gains an ever-refreshing pool of bonus dice.