Humphries survived one of the matches of the championship to edge past Gabriel Clemens 4-2 in a breathless, momentum-shredding contest that repeatedly threatened to swing away from the world number two before experience and timing finally dragged him across the line.
Humphries began with authority, seizing the opening set with a decisive break after Clemens missed chances at tops, pinning double four to establish early control.
The second set followed a similar pattern, Humphries accelerating through legs with heavy scoring and sharp finishing, averaging north of 109 and briefly appearing to be cruising.
What followed was a complete shift in tone. Clemens exploded into life in the third set, producing one of the finest passages of darts seen at this tournament.
Ton-plus finishes of 121 and 116 were delivered with conviction, capped by a stunning 125 checkout of bull, 25 and bull as the German averaged 115.62 for the set. Humphries, momentarily rattled, could only watch as the match tightened.
Humphries struck back in the fourth set with a breathtaking 170 checkout to level at two legs apiece, a finish that visibly jolted both the crowd and his opponent. Clemens responded without blinking, rattling in maximums and closing the set on double 10 to draw level at 2-2, having now won four legs on the spin.
Clemens broke again in the fifth set to move one leg from forcing a deciding set, but three missed set darts at tops proved costly, Humphries punishing the lapse by breaking back on double 16 before stepping up with a composed 81 checkout of 19, treble 12 and double 13 to finally shut the door.
Humphries finished with eight 180s, one of the tournament's standout Big Fish finishes, and a cluster of decisive checkouts under extreme pressure.
Clemens, meanwhile, produced one of the most entertaining performances of the event, matching and often exceeding the favourite for long stretches, landing nine maximums and repeatedly forcing Humphries into problem-solving mode.
'Made me work hard'
"I thought Gabriel got a lot better and made me work hard for it," Humphries told Sky Sports.
"If that double 13 didn't go on, it's 3-3, and I'm panicking! To get that double at the end, you see that celebration, that could be the difference between being a two-time world champion and not.
"Gabriel played fantastic there. He showed a lot of grit and determination, and I found that little level when I needed it, thank God!
"The trebles weren't going in for me as much as I wanted, but I found them in the right moments in certain parts. Gabriel found it every time. He put me under pressure, and that's what you need to do against me and Luke Littler.
"I'm really pleased to hit that massive shot, and I'm through to the next round.
"If my next opponent plays as Gabriel did, they will pose a few problems for me, but I enjoy playing in these games. It gives you a boost and a test."
Van Gerwen gets the job done
Michael van Gerwen booked his place in the fourth round of the PDC World Championship with a 4-1 victory over Arno Merk, producing a measured, increasingly authoritative performance to extinguish the resistance of the young German after a brief mid-match wobble.
Van Gerwen set the tone early, breaking immediately in the opening leg and racing through the first set with relentless scoring. A pair of maximums and tidy finishing, capped by a double 18 checkout from 36, gave the three-time champion a 3-1 lead and immediate control of the contest. Merk showed flashes of intent, but was repeatedly forced into chasing legs from a distance.
The second set followed a similar pattern. Van Gerwen maintained front-foot pressure, pinning D8 and D12 with minimal fuss to move two sets clear.
His scoring volume was doing the damage, keeping Merk pinned back and limiting opportunities on the outer ring despite the German beginning to settle into the occasion.
Merk briefly disrupted the flow in the third set, producing his best spell of the match. A superb 145 checkout and a clinical Shanghai 120 injected belief, and when Van Gerwen missed double 16 on 63, Merk pounced with a composed 67 finish to take the set and remind the crowd he was not finished.
Van Gerwen responded with focus rather than force, breaking early in the fourth set and capitalising as Merk's scoring dipped. A clean 55 checkout restored the two-set cushion, the Dutchman visibly tightening his grip as the finishing steadied.
Van Gerwen broke at the first opportunity in the fifth set, edged closer with a tops finish from 121, and then closed the match in fitting style, reducing 170 to 36 before pinning double 18 with his second dart to seal victory.
The Dutchman finished with a stack of maximums, consistent pressure on the German throw and a series of timely checkouts that ensured the match never drifted beyond his control.
Van Veen impresses again
In the opening encounter of the evening, Gian van Veen continued his serene progress at the PDC World Championship with a commanding 4-1 victory over Madars Razma, brushing aside a brief wobble to reach the fourth round in style and underline his growing credentials as a genuine contender.
Van Veen started with intent, breaking early in the opening set and capitalising on Razma's missed doubles to establish control. The Latvian showed flashes of resistance, including a tidy 109 checkout and a momentary nine-darter tease, but Van Veen's scoring power and cleaner finishing proved decisive as he edged the set 3-1.
The second set tilted the match firmly in the Dutchman's favour. Van Veen found another gear, breaking twice with authority and repeatedly reducing big numbers under no pressure. An 80 checkout and a clinical double 12 finish sealed the set, his composure contrasting sharply with Razma's growing frustration.
Any lingering doubt was removed in the third. Van Veen piled in his fourth maximum of the match and barely allowed Razma a look at a finish, tidying up 97 on tops to move within one set of victory. Razma was scoring solidly, but Van Veen was striking first and striking last.
Razma briefly disrupted the flow in the fourth set, producing his most dominant spell of the match. A confident 80 checkout and a 3-0 whitewash momentarily suggested a shift, as Van Veen's intensity dipped and his opponent finally imposed himself on the doubles.
The response was immediate and emphatic. Van Veen steadied, broke early in the fifth and closed the contest with the standout finish of the night, a superb 125 checkout via treble 20, treble 11 and double 16 to seal victory with a flourish.
Van Veen finished with four 180s, the highest checkout of 125 and long stretches of relentless control, never allowing the match to drift once momentum was reclaimed.
Earlier in the day, two-time champion Gary Anderson made it through to the fourth round of the World Darts Championship after beating Jermaine Wattimena 4-3 in a thriller at Alexandra Palace on Sunday afternoon.
Rob Cross hammered Damon Heta 4-0 to set up a showdown with defending champion Luke Littler in the next round, while Ryan Searle beat Martin Schindler by the same scoreline in the first match of the day.
Sunday evening session results
Gian van Veen 4-1 Madars Razma
Luke Humphries 4-2 Gabriel Clemens
Michael van Gerwen 4-1 Arno Merk