Su Yi poured practically all of his physical power and true essence into this one slash.

It seemed heaven and earth couldn’t bear it; the sword cut through them like a knife through canvas, and the resonant sword hum reverberated throughout the surrounding area. Dazzling sword qi blotted out almost the entire stretch of sky as it clashed with the six Unknown Dragons’ attacks.

Rumble!

Heaven swayed, the earth shook, and the moon and stars lost their radiance.

The distant onlookers’ fields of view went white as everything seemed to transform into endless chaos. Surging forces swept toward all sides.

From a distance, it seemed the entire stretch of sky was enveloped in currents of destructive energy. The air blazed with glowing light.

However, experts like the Cloudstone Venerate noticed that, despite this slash’s indomitable power, and although it broke through the six Unknown Dragons’ joint attack, Su Yi staggered and flew back.

He flew hundreds of feet before finally stabilizing himself!

The Cloudstone Venerate’s pupils constricted.

It was then that the onlookers’ field of view cleared up. They could see everything again, albeit barely.

Su Yi stood in the sky, hands behind his back. His face looked a bit pallid, but he was otherwise unharmed.

However, the six Unknown Dragons were smiling.

Their keen senses told them that Su Yi’s attack had drained what little remained of his true essence. He was already starting to show signs of weakness!

“This is bad!” Su Yi’s allies’ expressions changed, one by one.

They, too, could sense how flourishing Su Yi’s energy had been earlier, but now, it was as if he’d been sucked dry. He was practically hanging over a precipice!

“Excellent!” Lonely River, Yun Zhongqi, Shi Fengliu had been watching all this time, unmoving. Their hearts filled with excitement, and they were ready and raring to go, eager to strike at a moment’s notice.

How could they fail to realize that their opportunity had finally arrived?

“Fellow Daoist Su, your combat prowess is indeed heaven-defying, and your swordsmanship is without equal. The six of us struck together, yet you blocked our joint attack. I’m afraid that no one else in the Great Zhou could have done so. But now…

“You’re like a candle flickering in the wind,” said Zhou Changyi with a faint smile. “How much longer can you hold on?”

“It’s no wonder you put that cursed sword and black bell away earlier,” said Zhou Qingxuan leisurely, her gaze pitying. “It turns out… you don’t have the power to use such matchless treasures anymore.”

The other Unknown Dragons were smug too. They looked at Su Yi as if he were already dead.

However, out of caution, they were in no hurry to attack; they were worried about Su Yi’s final counterattack. 

By now, even those cultivators still in the Martial Dao could tell what was going on.

The combined strength of six Hidden Dragons was just far too terrifying!

They were a level stronger than even the possessed Su Hongli. Each wielded ancient, secret treasures and inheritances. Their cultivations and foundations were all at the peak of their respective realms!

By comparison, Su Yi’s aura was increasingly feeble; anyone could see that.

“Human power is limited. Fellow Daoist Su, even if your combat prowess were more heaven-defying than it already is, you only just overcame a grand battle. How could you possibly have the strength to fight on?”

Countless people sighed to themselves.

However, against all expectations, Su Yi only laughed. “A bunch of whetstones like you really think me such an easy target?”

As he spoke, he stretched, and a series of booms emanated from within his body, like the low rumbling of thunder.

His blue robes and black hair fluttered around him.

Beneath countless disbelieving gazes, Su Yi underwent rejuvenation. His depleted aura suddenly burst with an unstoppable wave of abundant energy. 

Boom!

In that moment, Su Yi underwent metamorphosis, like a butterfly emerging from its cocoon. Throughout his body, his skin, tendons, flesh, bones, meridians, acupoints, and organs… Every inch of him lit up, inside and out.

Clear Dao Light coursed through him and filled his surroundings, as sudden and forceful as an avalanche. He lit up like the sun, single-handedly illuminating this entire stretch of sky!

The origin energy lingering above the Jade Capital swept in from all sides, as if something were calling to it. It surged like mad into Su Yi’s body, visible even to the naked eye. 

Rumble~        

The place where Su Yi stood transformed as a vast and shocking windstorm of origin energy formed around him!

“This….” Some people stared, wide-eyed, rooted the spot, as if gazing upon a god. 

“The signs of a breakthrough!” Someone gasped, and his expression changed dramatically. “He’s using combat to realize a breakthrough in his cultivation? That’s amazing!”

The anxious Cloudstone Venerate was already planning to intervene when he saw this. His eyes lit up, but his heart filled with astonishment.

Not even he would have guessed that, just as it seemed there was no way left, Su Yi would break through in one fell swoop and enter the Xiantian Martial Ancestor Realm!

When he saw this, the six Unknown Dragons’ expressions changed dramatically, filling with shock and rage, as if they’d seen a ghost.

“Dammit!”

“Just now, this punk was using us as stepping stones to help him break through!”

“Hurry! Kill him while he’s still only just broken through, before his cultivation stabilizes!” Zhou Changyi bellowed, and his expression surged with killing intent. His earlier leisurely composure disappeared without a trace.

“Alright. Everyone, attack together!” The others nodded, one after another.

Boom! Zhou Changyi was the first to attack. He waved Purple Lightning and circulated his cultivation, unleashing his trump card without the slightest hesitation.

He dared not hold back; once Su Yi stabilized his cultivation as a Xiantian Martial Ancestor, his strength would inevitably be even more terrifying than before!

“Get him!” The other five Unknown Dragons reached the same conclusion, and all of them readied their strongest killing techniques.

Six Unknown Dragons, each in possession of secret arts and treasures, were all attacking at once. How shocking of a scene would this be? 

Everyone watched as—

Rumble! Boom!

Sword qi filled the air, a saber’s edge glinted, Buddhist imprints boomed, wind and lighting ran rampant…

Secret arts and treasures of all kinds burst forth, like floodwaters through a dam, a grand spectacle sweeping through the sky. Beneath the onslaught of destruction, the entire stretch of heaven and earth showed signs of imminent collapse.

Practically simultaneously, Lonely River took out a red alms bowl, which expanded in mid-air. A dazzling, unstoppable arc surged from its interior.

Yun Zhongqi’s eyes crackled with electricity, and he bellowed, activating the Daoist insignia in his hand. It bore down on the sky like a primordial divine mountain.

Shi Fengliu took a deep breath, then took out a silver flying sword, which struck like lightning.

The Pineflame Daoist waved his sleeves, and a dragon of pure fire streaked through the air, forming a vast and explosive Fire Dragon Array.

Chang Guoke’s eyes bulged, and he felt as if a knife were twisting in his heart. He would never have guessed that even his master would get involved and fight alongside the other Earthly Immortals.

Qing Jin hadn’t anticipated this either, and she stood there, rooted to the spot. 

It was at that moment that Su Yi put away the Abstruse God Sword, and his deep gaze filled with indifference. He now longer showed even the slightest ripple of emotion.

Killing these old dogs was nothing; they weren’t even qualified to make him draw his sword.

Boom!

He suddenly threw a punch. 

He’d already undergone metamorphosis to reach the Xiantian Martial Ancestor Realm, filling this simple, unadorned punch with power.

When the fist force shot through the sky, heaven and earth trembled. The power of their surroundings gathered within the clear fist force, like a minister submitting to its king.

Watching from a distance, the power of this punch seemed to bore a hole through heaven and earth, collapsing the skies!

If forced to describe it, one might call it a “Dao punch”!

This was because the power infused into this fist surpassed the usual ranking system of xiantian qi. This was the Dao rank!

Boom!

Heaven and earth trembled. 

Su Yi’s fist forged straight ahead, generating enough wind to disperse the clouds and suppressing the surrounding skies. Attacks were flying toward Su Yi from all sides, but it exploded right through them.

Like an axe through bamboo!

The six Unknown Dragons, as well as Lonely River and the various Earthly Immortals, were all visibly shocked. Their faces filled with disbelief.

They wouldn’t have guessed that, so soon after breaking through, Su Yi’s fist would be this strong! 

The distant onlookers were deeply shaken too. Their eyes widened, and their jaws hung slack.

This change had come too suddenly.

Earlier, Su Yi was like a candle flickering in the wind, exhausted to the point of collapse. Now, in the blink of an eye, he’d broken through the upper limit of the Grandmaster Realm, leaping into the ranks of Xiantian Martial Ancestors!

The power of his fist was like that of a deity!

“Everyone, if we don’t work together, I’m afraid he’ll turn the tides on us!” Zhou Changyi spat through gnashed teeth, his expression terrifyingly dark.

“Kill him!” As if through some tacit misunderstanding, both the Unknown Dragons and the Earthly Immortals all struck with full force.

“Nothing but a bunch of mantises trying to block a chariot.” Su Yi shook his head.

He’d already become a Xiantian Martial Ancestor, so he naturally wouldn’t waste any more time. From this moment forth, he’d no longer hold anything back.

Bang!

Xiantian qi flowed around his tall, lean figure, radiant and ethereal, shimmering with Dao light. 

How terrifying was Su Yi when he went all out?

The onlookers quickly saw the answer for themselves.

Boom!

A violent blast rang out in midair.

In half the time it took to snap one’s fingers, Su Yi was right in front of his nearest foe, Zhou Shanjia.

Despite his powerful and despotic body-refining and cultivation, he only just barely managed to raise his palm and unleash a defensive Buddhist secret art.

A golden light barrier appeared, like a bell, protecting Zhou Shanjia on all sides. Sanskrit chanting emanated from the golden light, like the roars of dragons and tigers.

The faint image of an arhat riding a fierce tiger, a golden dragon wrapped around him, appeared within the golden light. 

The Brahma Golden Bell!

This was an ancient Buddhist legacy with incomparably shocking defensive power!

But when Su Yi’s punch came crashing down—

Bang!

A deafening blast followed.

The incomparably miraculous Brahma Golden Bell shattered like glass. One punch, and it burst.

Immediately afterward, a series of cracks rang out as Zhou Shanjia’s prayer beads, robes, weapon, and protective treasures burst, unable to bear such intense fist force.

Finally, Zhou Shanjia flew back like an arrow, flying over a thousand feet away before just barely managing to stabilize himself. 

His face was pallid, his eyes dim, and his aura was feeble. Blood poured from his lips in a non-stop stream.

There was a three-inch deep fist imprint on his chest, right over his heart!

“I… I couldn’t block that punch?” Zhou Shanjia’s eyes filled with bewilderment.

Then, beneath the crowd’s dumbstruck gazes, the man with a body like an invincible golden vajra split apart in midair!

Whoosh!

Hunks of blood and flesh plummeted down to earth.

The sight of such a bloody demise made countless people’s hair stand on end. They couldn’t help but gasp.

An Origin Dao cultivator who practiced an ancient Buddhist inheritance couldn’t even block a single casual punch from Su Yi?

The golden bell here looks like a reference to a real Shaolin training exercise, "covering with a golden bell." Of course, the real-life version is different from the fictional version, but I'll include some info on both below. The real version is a training method that makes you "invulnerable", or at least more durable, while the fictional version can be either a stronger version of the real thing, or a technique that manifests a barrier-like bell as a way of defending the user.

Let's start with the real thing: 

Here's a blog post on the subject. Goes into the history a bit, but also into the gap between reality and expectations and the exaggerated way in which people talk about martial arts. A quote : "If you practise this method for two or three years, your breast and your back will become strong like stone or iron; it is of no importance whether the enemy punches or kicks, it will do no harm. Even a sword blow will not do any injury to a man who practices the skill of “Gold Bell.”" 

This article talks about its practical applications for martial arts and self-defense. Unlike the other article, this one seems to have nothing but good things to say about the Golden Bell.

Here's a video. Not much info, but you might enjoy someone punching someone else, only to complain that his hands hurt. 

The fictionalized version is more like this, or this, or this.