The Enneagram is a personality profile consisting of nine personality types.  I find it helpful in creating realistic characters, in that it is not a static system, but one that details the way that certain personalities evolve, devolve, or change in circumstances of stress, chaos, and breakdown or growth, development, acceptance, and wholeness.  "In other words, different situations will evoke different kinds of responses from [a specific] personality."*  Each of the nine types can have some aspects of its neighboring type (called a wing).  This results in the 27 types below (listed with a title that is sometimes helpful, sometimes a bit misleading).  The descriptions of the 9 basic types may be found below the list of the 27.

There is no right or wrong, good or bad personality type.  Because the system is dynamic, you may find a Type 1 (The Idealist) that is "extraordinarily wise and discerning...Conscientious with strong personal convictions: they have an intense sense of right and wrong, personal religious and moral values. Wish to be rational, reasonable, self-disciplined, mature, moderate in all things.  Extremely principled, always want to be fair, objective, and ethical: truth and justice primary values. Sense of responsibility, personal integrity, and of having a higher purpose often make them teachers and witnesses to the truth."  Conversely, a more depraved or immature Type 1 Idealist could be "highly dogmatic, self-righteous, intolerant, and inflexible. Begin dealing in absolutes: they alone know "The Truth." Everyone else is wrong: very severe in judgments, while rationalizing own actions.  Become obsessive about imperfection and the wrong-doing of others...Become condemnatory toward others, punitive and cruel to rid themselves of 'wrong-doers.'" 

The Idealist - 1 with a 9 wing
The Reformer - 1
The Advocate - 1 with a 2 wing
The Servant - 2 with a 1 wing
The Helper - 2
The Host/Hostess - 2 with a 3 wing
The Charmer - 3 with a 2 wing
The Achiever - 3
The Professional - 3 with a 4 wing
The Aristocrat - 4 with a 3 wing
The Individualist - 4
The Bohemian - 4 with a 5 wing
The Iconoclast - 5 with 4 wing
The Investogator - 5
The Problem Solver - 5 with a 6 wing
The Defender - 6 with a 5 wing
The Loyalist - 6
The Buddy - 6 with a 7 wing
The Entertainer - 7 with a 6 wing
The Enthusiast - 7
The Realist - 7 with an 8 wing
The Maverick - 8 with a 7 wing
The Challenger - 8
The Bear - 8 with a 9 wing
The Referee - 9 with an 8 wing
The Peacemaker - 9
The Dreamer - 9 with a 1 wing

Type One in Brief   The Idealist

Ones are conscientious and ethical, with a strong sense of right and wrong. They are teachers, crusaders, and advocates for change: always striving to improve things, but afraid of making a mistake. Well-organized, orderly, and fastidious, they try to maintain high standards, but can slip into being critical and perfectionistic. They typically have problems with resentment and impatience. At their Best: wise, discerning, realistic, and noble. Can be morally heroic.

    * Basic Fear: Of being corrupt/evil, defective
    * Basic Desire: To be good, to have integrity, to be balanced
    * Enneagram One with a Nine-Wing: "The Idealist"
    * Enneagram One with a Two-Wing: "The Advocate"

Key Motivations: Want to be right, to strive higher and improve everything, to be consistent with their ideals, to justify themselves, to be beyond criticism so as not to be condemned by anyone.

Type Two in Brief   The Helper

Twos are empathetic, sincere, and warm-hearted. They are friendly, generous, and self-sacrificing, but can also be sentimental, flattering, and people-pleasing. They are well-meaning and driven to be close to others, but can slip into doing things for others in order to be needed. They typically have problems with possessiveness and with acknowledging their own needs. At their Best: unselfish and altruistic, they have unconditional love for others.

    * Basic Fear: Of being unwanted, unworthy of being loved
    * Basic Desire: To feel loved
    * Enneagram Two with a One-Wing: "Servant"
    * Enneagram Two with a Three-Wing: "The Host/Hostess"

Key Motivations: Want to be loved, to express their feelings for others, to be needed and appreciated, to get others to respond to them, to vindicate their claims about themselves.

Type Three in Brief   The Achiever

Threes are self-assured, attractive, and charming. Ambitious, competent, and energetic, they can also be status-conscious and highly driven for advancement. They are diplomatic and poised, but can also be overly concerned with their image and what others think of them. They typically have problems with workaholism and competitiveness. At their Best: self-accepting, authentic, everything they seem to be—role models who inspire others.

    * Basic Fear: Of being worthless
    * Basic Desire: To feel valuable and worthwhile
    * Enneagram Three with a Two-Wing: "The Charmer"
    * Enneagram Three with a Four-Wing: "The Professional"

Key Motivations: Want to be affirmed, to distinguish themselves from others, to have attention, to be admired, and to impress others.

Type Four in Brief   The Individualist

Fours are self-aware, sensitive, and reserved. They are emotionally honest, creative, and personal, but can also be moody and self-conscious. Withholding themselves from others due to feeling vulnerable and defective, they can also feel disdainful and exempt from ordinary ways of living. They typically have problems with melancholy, self-indulgence, and self-pity. At their Best: inspired and highly creative, they are able to renew themselves and transform their experiences.

    * Basic Fear: That they have no identity or personal significance
    * Basic Desire: To find themselves and their significance (to create an
         identity)
    * Enneagram Four with a Three-Wing: "The Aristocrat"
    * Enneagram Four with a Five-Wing: "The Bohemian"

Key Motivations: Want to express themselves and their individuality, to create and surround themselves with beauty, to maintain certain moods and feelings, to withdraw to protect their self-image, to take care of emotional needs before attending to anything else, to attract a "rescuer."

Type Five in Brief   The Investigator

Fives are alert, insightful, and curious. They are able to concentrate and focus on developing complex ideas and skills. Independent, innovative, and inventive, they can also become preoccupied with their thoughts and imaginary constructs. They become detached, yet high-strung and intense. They typically have problems with eccentricity, nihilism, and isolation. At their Best: visionary pioneers, often ahead of their time, and able to see the world in an entirely new way.

    * Basic Fear: Being useless, helpless, or incapable
    * Basic Desire: To be capable and competent
    * Enneagram Five with a Four-Wing: "The Iconoclast"
    * Enneagram Five with a Six-Wing: "The Problem Solver"

Key Motivations: Want to possess knowledge, to understand the environment, to have everything figured out as a way of defending the self from threats from the environment.

Type Six in Brief   The Loyalist

The committed, security-oriented type. Sixes are reliable, hard-working, responsible, and trustworthy. Excellent "troubleshooters," they foresee problems and foster cooperation, but can also become defensive, evasive, and anxious—running on stress while complaining about it. They can be cautious and indecisive, but also reactive, defiant and rebellious. They typically have problems with self-doubt and suspicion. At their Best: internally stable and self-reliant, courageously championing themselves and others.

    * Basic Fear: Of being without support and guidance
    * Basic Desire: To have security and support
    * Enneagram Six with a Five-Wing: "The Defender"
    * Enneagram Six with a Seven-Wing: "The Buddy"

Key Motivations: Want to have security, to feel supported by others, to have certitude and reassurance, to test the attitudes of others toward them, to fight against anxiety and insecurity.

Type Seven in Brief   The Enthusiast

Sevens are extroverted, optimistic, versatile, and spontaneous. Playful, high-spirited, and practical, they can also misapply their many talents, becoming over- extended, scattered, and undisciplined. They constantly seek new and exciting experiences, but can become distracted and exhausted by staying on the go. They typically have problems with impatience and impulsiveness. At their Best: they focus their talents on worthwhile goals, becoming appreciative, joyous, and satisfied.

    * Basic Fear: Of being deprived and in pain
    * Basic Desire: To be satisfied and content—to have their needs
          fulfilled
    * Enneagram Seven with a Six-Wing: "The Entertainer"
    * Enneagram Seven with an Eight-Wing: "The Realist"

Key Motivations: Want to maintain their freedom and happiness, to avoid missing out on worthwhile experiences, to keep themselves excited and occupied, to avoid and discharge pain.

Type Eight in Brief   The Challenger

Eights are self-confident, strong, and assertive. Protective, resourceful, straight-talking, and decisive, but can also be ego-centric and domineering. Eights feel they must control their environment, especially people, sometimes becoming confrontational and intimidating. Eights typically have problems with their tempers and with allowing themselves to be vulnerable. At their Best: self- mastering, they use their strength to improve others' lives, becoming heroic, magnanimous, and inspiring.

    * Basic Fear: Of being harmed or controlled by others
    * Basic Desire: To protect themselves (to be in control of their own life
          and destiny)
    * Enneagram Eight with a Seven-Wing: "The Maverick"
    * Enneagram Eight with a Nine-Wing: "The Bear"

Key Motivations: Want to be self-reliant, to prove their strength and resist weakness, to be important in their world, to dominate the environment, and to stay in control of their situation.

Type Nine in Brief   The Peacemaker

Nines are accepting, trusting, and stable. They are usually creative, optimistic, and supportive, but can also be too willing to go along with others to keep the peace. They want everything to go smoothly and be without conflict, but they can also tend to be complacent, simplifying problems and minimizing anything upsetting. They typically have problems with inertia and stubbornness. At their Best: indomitable and all-embracing, they are able to bring people together and heal conflicts.

    * Basic Fear: Of loss and separation
    * Basic Desire: To have inner stability "peace of mind"
    * Enneagram Nine with an Eight-Wing: "The Referee"
    * Enneagram Nine with a One-Wing: "The Dreamer"

Key Motivations: Want to create harmony in their environment, to avoid conflicts and tension, to preserve things as they are, to resist whatever would upset or disturb them.