Just for a heads up, the “Ultimate Master” or the “Old Man on the Mountain” is usually referencing Eastern mysticism and is a long standing genre convention in cinema. When used in fiction, it always involves some kind of pilgrimage. It also has roots in reality, enough so that a whole genre of Chinese cinema builds itself around the concept.
Now, other cultures have this concept too, and there are European branches that defy what has become the expected fictional norms. However, when you decide to follow this train of thought for your character, it’s important to recognize what the trope is, where it comes from, and what its hallmarks and audience expectations are.
If you don’t want to write a character for whom their martial arts training is a quasi-religious experience, grounding itself in philosophy and spirituality, then this trope is not for you.
In a simple, much more recognizable Western example, if you don’t imagine yourself writing a Jedi then this trope is not for you.
9/10 that’s pretty much what the trope is, and, real talk, the more spiritual side of martial arts can do some pretty crazy shit in reality. I’ve seen American martial arts masters bend rebar with their clavicles, break baseball bats with their shins, break ten bricks with their hands, and that’s the more commonplace energy manipulation you’ll see in a standard martial arts school far from their traditions.
The conceptual idea that martial arts give you superpowers is rooted in the real world. Dragon Ball Z for example, takes real world martial arts philosophies and dials them over 9,000. Yoda in The Empire Strikes Back utilizes real philosophy with real world application when training Luke. For Lucas, this is mostly by accident but nevertheless if you’ve ever been in martial arts training Yoda sounds suspiciously similar.
The philosophy at play is spiritual/religious in nature, but also real. The idea is that through training, you will reach a point of inner spiritual ascension. Upon taking this first step in understanding, you reach a new plateau of spiritual and physical harmony that is beyond what the average martial artist can access. (Ronin Warriors) That’s what the mountain training is about, that’s what its for, and that’s why the neophyte is not usually the one who seeks out the Wise Man on the Mountain. (Yu Yu Hakusho) Usually, its a secondary or tertiary step in your training. You go to the mountain when the time comes to look inward, rather than outward. When you want to face yourself.
The other version of this trope is you have a character who was taken in by the Man on the Mountain as a child and raised in a hereditary martial art until they leave (Rurouni Kenshin), to test themselves out in the world. Where they go out and find other martial artists and, for whatever reason, fight them as a test of their abilities. (Crouching Tiger, Hidden Dragon) Or they are sent out into the world on some kind of a mission. (Iron Fist, The Empire Strikes Back) If you have watched any amount of shounen/fighting anime or any wuxia cinema, I guarantee you’ve seen this one before.
You’re basically talking about people who spend their whole lives training, and who are going to be fighting a lot. You want to fight the guy who learned to channel themselves in meditation while standing in a freezing waterfall for four to six hours? No, you don’t, especially when you know the purpose of meditation in martial arts. These are the guys with the ability to balance themselves on the top of their head. Its also worth pointing out that the balancing on the head has a real combat application, the purpose is to train balance and physical control. If this person can achieve perfect balance on their head, what are you going to do about knocking them over when they’re actually on their feet? These are kinds of skills you will never achieve unless you’ve spent a significant portion of your life in isolation training your body to a level of physical excellence that is so far beyond the average you seem superhuman.
This is the level above Jet Li playing the villain in Lethal Weapon 4, where it’s all normal and then… wham. Try to remember too, when you’re watching any Jet Li, Jackie Chan, or Donnie Yen film, that the camera is often losing frames on their fight sequences because they are moving too fast for it to follow. Or they are slowing way down.
That’s just approaching pinnacles of excellence in performance martial arts.
It’s worth thinking about it this way, you’ve got a character who goes up to the mountain and comes back. They’ve spent their years, paid their dues, put in the time, and achieved that pinnacle. Now, the rest of the world is moving in slow motion. Physically, mentally, spiritually, they have reached a plateau beyond what the other (standard) combatants are capable of. These enemies are slower, less aware, riddled with flaws, and do not make the most of their energy. They also adjust faster to new challenges as they test themselves in the world at large.
The Man on the Mountain isn’t classroom training. It is not a safe environment. It is one part martial training, one part spiritual exercise, and one part survival training. What happens on the mountain is never standard martial arts training, it is never safe. Whether it’s what you saw in Mulan, hopping over a raging river from pole to pole the size of your foot, fishing from the river with your hands, or any number of other countless exercises you’ve seen in anime and martial arts movies that were glossed over. The jacket routine in Jackie Chan’s The Karate Kid which culminates in this sequence. (Did you know The Karate Kid is an Old Man on the Mountain movie? All of them are.) Some of those techniques may have looked really dumb, but most of them had a purpose.
This is about testing yourself beyond your limits.
It’s the quintessential difference between student and master.
So, do they have weaknesses? Not if the master knew what he was doing. If he or she didn’t, if they were dicking around or the training didn’t properly sink in, then yeah, they’ll have lots of weaknesses. If not, they’re moving into the territory One Punch Man is subverting, mocking, and critiquing.