Luke Humphries produced one of the most remarkable escapes seen on a stage to beat Joe Cullen 4-3 in a sudden-death thriller.
Humphries looked down and out as Cullen threw for the match at 2-0 in the final set, but it developed into an all-timer which Humphries won with a 100 checkout on double 10.
At 2-0 in front, Cullen paid the price for six visits without bettering 60 as Humphries was able to break in 17 darts, before Cullen then missed two match darts at double 18 by the barest of margins.
Cullen responded to that with a 116 finish to lead 3-2 and was sat on 44 for the match in the following leg when Humphries hit tops-tops for a 100 checkout to somehow stay alive.
After a regulation Cullen hold, Humphries then hit 86 in two darts with his opponent waiting on 50, and the world number three looked to have finally broken Cullen when hitting double two for a break of throw.
But Humphries then hit double 12 when he needed the adjacent double five to win, before missing six more darts at the same double as Cullen this time came back from the brink to force sudden death.
With the darts in his favour it was Cullen who held the advantage once more, but he couldn't threaten with 121 left and that left Humphries on 100 once more, this time pinning double 10 to end an epic.
"Want to feel my heart? It's gone," said Humphries. "I don't know what to say. I don't want to make too many big statements, but that's one of the best games I've been a part of.
"I feel so sorry for Joe. Sometimes in darts there doesn't deserve to be a loser, and I don't think Joe deserved to lose that game.
"I was under pressure and I felt it. I'm human. He put me under real pressure there and that's credit to him. What a game of darts, it's great to be involved in.
"I love Joe to pieces. He was so unlucky, I thought that was a great game."
Luke Littler put in another sensational display to beat Raymond van Barneveld 4-1 in a high-quality match and will now be favourite to reach the semi-finals aged 16.
Littler averaged 105 against his veteran opponent, who played to a high standard himself but was made to look ordinary by a youngster living the dream at Alexandra Palace.
After being bullied early on, van Barneveld pinched set four to avoid a whitewash but Littler was unaffected as he came out and held throw, hitting double 15 with his first match dart to reach the quarter-finals.
"Unbelievable, I don't know what to say," was Littler's response when asked how it felt to beat his darting idol.
"I was just thinking, three legs away, one set away, and I've done it.
"(van Barneveld) said 'you can go all the way, I hope you do go all the way'. He's a true gentleman and I respect Raymond.
"I just looked at the draw. I fancy myself, I do fancy myself.
"It's unbelievable. I'm just so glad to get over the line. After I do all the media I'll go see my family and just chill out now."
Littler stormed out of the gates to win the first set with a 104 average, capping it with a 12-dart leg, and pegged another to see out set two in similarly dominant fashion.
With his average remaining in three-figures throughout, Littler made it 3-0 when pinning tops to take a deciding leg for the third set, as van Barneveld kept throwing punches without landing in the face of a remarkable display.
The Dutch legend deservedly got on the board when hitting double six to take another deciding leg for the fourth set, but any sense of Littler stalling with the winning line in sight proved unfounded.
Littler threw an 11-dart leg to move within one of the match and while van Barneveld made him wait, Littler dominated what proved to be the final leg as he sensibly declined the chance to close it out with a 170 finish, instead hitting double 15 to power his way into the last eight.
Brendan Dolan fended off a Gary Anderson fightback to win 4-3 and reach his second World Championship quarter-final, where he'll face Littler.
Dolan had dominated early, winning eight of the first nine legs, but when Anderson hit bull to hold throw in the deciding set having turned the match around, he looked set to take over at last.
Dolan opened the following leg with throws of 54, 60, 45 and 58, handing the darts to Anderson, but after the Scot left 11 and couldn't take it out, Dolan pinned double 12 to move within one of the match.
Anderson was again ahead in the leg, this time throwing first, but Dolan's 200th maximum of the season could not have been better timed and left him needing 63 after Anderson hit the wrong side of the wire when attempting to take out 128.
When Dolan missed two darts for the match Anderson looked set to escape, but couldn't hit double five as Dolan returned to find the centre of the double three bed for a famous win.
"When you're on double three, you wonder what to do. I hit double three to beat Michael van Gerwen at the Match Play; I said (to myself) be brave, go for it. I was assertive, went for it, and hit it.
"That was some game. It was really tough because I mentally collapsed when I was 2-0 up and went two legs up in the next set.
"I was wondering what was wrong with Gary, and I fell in to the trap of thinking he wasn't at it, and then he started to come back. I thought at least fight, make him win it.
"I played one of the greats of the game in my lifetime. To compete with them, just to play with them is an hour; to actually beat them in big games is an awesome feeling."
On who he'll face next, either the legendary Raymond van Barneveld or emerging star Luke Littler, Dolan confessed that he expected not to be receiving much more support than he did against the ever-popular Anderson.
"The crowd wasn't with me tonight, and I expect the crowd not to be with me the next night!" he added.
More to follow
Rob Cross moved through to the quarter-finals for the first time since he lifted the trophy in 2018, averaging almost 99 to seal a straight-sets victory against a struggling Jonny Clayton.
Cross kicked off proceedings with a 140 outshot – the same finish he landed to win the Sid Waddell Trophy almost six years ago – and that set the tone for a dominant display as he progressed to a last-eight clash against Chris Dobey.
In Saturday’s opener, Scott Williams lived up to his showman reputation as he dumped out 10th seed Damon Heta to set up a tussle against three-time champion Michael van Gerwen.
Williams started strongly, claiming the opening set before raising the roof midway through the second with a 170 checkout, only for Heta to restore parity with a timely 12-darter.
However, the Australian never recovered from spurning three darts to lead 2-1, and a fearless Williams added 108 and 110 checkouts to his highlights reel to continue his run at Alexandra Palace.
Meanwhile, Dave Chisnall won a gruelling six-set affair against Daryl Gurney to progress to the quarter-finals for the fourth time in his career.
Chisnall fought his way into a two-set lead before Gurney responded with stunning 130 and 151 finishes to level, but the 2021 semi-finalist hit back by winning six of the next seven legs to triumph.
Saturday December 30
Afternoon Session (12.30pm GMT)
Fourth Round (Best of 7 sets)
TV Coverage: Sky Sports Darts
Evening Session (7pm GMT)
Fourth Round (Best of 7 sets)
TV Coverage: Sky Sports Darts