"...let go your conscious self and act on instinct." -- Ben Kenobi
Types 8, 9, and 1 make up the intuition triad of the Enneagram, also known as the body triad because of the tendency of people in this group to say things like, "I knew it in my gut." Reactions can be very instinctual, requiring little thought and ignoring emotions. Intuition isn't well understood by science. It's the brain making a "leap of logic" and, while some studies have shown that forcing people to do something like math intuitively generates more correct responses than people who are required to "logic it out," that does not mean that people who rely on intuition are always right. It's very dependent upon the individual. The motivating emotion for this triad is anger, but it manifests differently for each of the three types (unlike for the intellectual triad where their fear is almost always about decision-making).
When you think of the stereotypical, emotionally-detached father-figure who expects and demands unquestioning loyalty and obedience, you are thinking of the type Eight. Eights want to be "in charge," hence the title of "The Boss." They are also know as the Challenger, because they frequently put themselves in positions of challenging authority. It's hard to be in charge when someone else is telling you what to do so they have a tendency to defy authority just for the sake of doing it. This is your true rebel without a cause.
However, this is not the loner rebel out doing his own thing. Eights are almost always extroverts and often charismatic. As such, they are frequently able to gather followers for whatever it is they're doing, leading a rebellion or not.
More than anything else, the Eight wants to be in charge of his own destiny. As such, he hates to have his authority questioned. Above all else, the Eight believes in his own "rightness," whether or not there is anything with which to back up his views. This is what makes him, in his own mind, more suited than all others to be the one in charge. Questioning his authority is equivalent to questioning your own loyalty to him but, even worse, you may cause him to question himself and his own qualifications for leadership. Eights are adept at burying their own doubts, though, and proceeding with confidence, one of the qualities that make people look up to them. No matter if his path is correct or not, he will tread it boldly.
In an effort to be in control of all things and not allow anyone to have power over them, Eights are emotionally unavailable. Love, especially, can give someone else power over them or make them appear weak, so they keep their emotions as bottled up as possible. This can lead them to reject others preemptively. It's better to cut people out when they are in control of the situation rather than to risk being hurt and losing control to someone else or in front of other people.
The typical response to any sort of threat, real or imagined, to the Eight's authority, which can include anything from an actual challenge to just making him look bad in some way, is anger. Anger is the first defense mechanism of the Eight. And the first offense mechanism. It is through anger that the Eight dominates his "foes."
At their best, Eights can fight the "good fight" and do a lot of good. They are willing to protect "their people," because they willingly give back the loyalty they receive. They can come to understand that they can't please everyone (not that they're trying to) and learn to take some amount of criticism without feeling threatened. Often, this state is achieved through surrendering themselves to some higher authority or ideal.
At their worst, they become dictators, believing completely in "might makes right." They use force and violence to inflict their will upon the ones under their power.
It should be noted that Eights are almost always men (just as Twos are almost always women). It's unclear whether this is because Eight behavior in women is culturally unacceptable and, thus, they are "broken" of it early on in life.