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When you watch Justin Gaethje (18-0, 15 KO) fight, the eyes tell the story. There are his, filled not with anger, but with nothing at all. A cold, deep void, bottomless and unyielding.

Then there are his opponent's, wide, in awe, knowing they've stared into the soul of a predator and slightly uncomfortable with what that means. They are the eyes of a man who may have entered a steel cage expecting an athletic contest.

He will leave knowing he's been in a fight instead.

Gaethje, who will face off with former lightweight champion Eddie Alvarez on Saturday at UFC 218, is violence personified. He's what politicians feared when they banned the sport of mixed martial arts across the country in the 1990s, a man unafraid of his own potency and the potential consequences of his actions, comfortable with the problems his sledgehammer fists create every time he touches another man's body.

Jack Slack, one of the sport's great analysts, calls Gaethje "hypnotic." A fighter who seeks out and thrives in the chaos many others spend their professional lives hoping to avoid:

"...He is always flirting with absolute disaster. He is an accomplished wrestler who can stuff the best shots from even bad positions, and yet he insists his fights be contested on the feet and takes great pride in his record there. But he also does a ton of things which get him into trouble and force him to fight uphill. A man of Gaethje's ability who fought more conservatively might not get the knockouts, but he would be cruising past the competition with little difficulty. It seems as though it is Gaethje who provides all of the back-and-forth in his fights."

For years, MMA has been dominated by the absence of violence. The sport as it exists in 2017 is mostly a 25-minute exercise in avoiding problems. Only when an opponent gets tired, impatient or sloppy do the modern greats strike.

Many of the best UFC fighters are not the athletes most capable of dismantling and dispatching their foes. They are, instead, the men and women best able to mitigate the risks their opponents present. The one slick enough to avoid damage and danger.

A former NCAA All-American wrestler at the University of Northern Colorado, Gaethje could easily take that approach too. He could use his grappling acumen to ensure he remains in control, piling up points carefully, striking only when expedient and safe.

Instead, he's a man on a mission to deliver violence in uncomfortable proximity, a fighter who starts in your face and makes a concerted effort to never allow you to be more than a couple of steps away.

His dad worked for decades in a copper mine. His twin brother does too. Gaethje himself spent a long summer there. He knows darkness and tight quarters; they're ingrained in his soul. A fight is merely a way to celebrate it. A song of violence, of blood, of danger and despair.

A fight with Gaethje doesn't look like anything else you'll see on a UFC card. Perhaps that's why he exploded as an underground, grassroots sensation on the independent circuit. Each of his World Series of Fighting bouts was a reunion of sorts for the sport's hardcore fans who saw glimpses of the familiar in his uncomplicated approach.

Gaethje may be the future of the lightweight division. But he's also the past. His are the blistering lowkicks of Marco Ruas, thrown with the confidence of a man with the wrestling chops to avoid all but the best takedown attempts. The kicks alone can end a fight, but their main purpose is to drive an opponent back into the cage.

That's where Gaethje does the kind of work that can be uncomfortable, not only to receive, but even to bear witness to.

Some avoid it for a time, skirting around the cage in a desperate backwards race from a man who will never stop coming. Like a horror-movie villain, Gaethje thrives on this fear, stalking, ever stalking, until a man has no choice but to stand and fight.

"When you fight me, you aren't going to be able to be so careful," he told me in a 2015 interview. "They better block their face and knock me out. I'm going to hit them, kick them. I'm going to come forward. They'll have to run, literally run, backwards. That's the only way to get away from me. And eventually you're going to run into the cage."

Michael Johnson, Gaethje's opponent in his first UFC fight in July, saw all the flaws in his style.

"He hasn't been at this level," Johnson told Fight Society's Damon Martin. "He hasn't been with the bright lights, he's great at what he does, but he might be out of his league on this one."

In a sense, Johnson was exactly right. Gaethje is a flawed, reckless fighter. He does take a lot of shots. Johnson did hit him with everything he had, wobbling him on multiple occasions.

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It's just didn't matter. Gaethje survived all Johnson could offer. Johnson couldn't say the same.

From such tactics, legends are born.

Gaethje accepts he's going to get hit. His style demands it. He even accepts that one day he's not going to get up from one of the many punches that finds its way to his chin. It's from that acceptance that greatness springs, allowing him the freedom to throw himself into harm's way, betting big that he will finish you before you can end him.

"A lot of people say I'm reckless and I take too many shots," he told me. "I take shots on the forehead. There's nothing wrong with that. It puts me in punching range.

"When I take a right hand, I roll with it. I don't absorb every single bit of the punch. There's different ways to alleviate some of the force of a punch besides just getting out of the way. When I take it, it's on my gloves. I don't get hit a ton on the button. When I do get hit, I feel like I'm setting myself up for big shots."

Alvarez, Gaethje's opponent, is no stranger to this sort of battle. A former champion, he's famous for his own back-and-forth contests, occasionally losing himself in a kind of bloodlust. In recent days, the two men have taken to arguing about who is the more violent fighter.

It's the kind of conversation that should be music to a fight fan's ears. Neither are articulate wordsmiths like Conor McGregor. They don't have the unhinged, oddly pure, anger that drives a Diaz brother. They are simply fighters.

Sometimes that's enough.

Jonathan Snowden covers combat sports for Bleacher Report.