It's dangerous and all but extinct from WWE, but blood is still an impactful narrative tool for the stories told between the ropes.
Over the last five years, WWE has been mostly cleansed of its macabre past. Bleeding to enhance the drama of a match is now a rarity. Extreme Rules, the night where WWE turns up the intensity, may be the best chance for fans to see bloodshed in a WWE ring for a while.
Last year, Brock Lesnar and John Cena's battle ended with both men reddened by wrestling's powerful prop. Lesnar busted his head open earlier this year in order to elevate the ferocity of his rivalry with Triple H.
Blood has been used to excess in the past. Cutting one's self for the sake of the audience's entertainment can end in mangled foreheads or it may lead to the spread of disease (h/t CagesideSeats.org).
Used sparingly, blood can be a tangible way to show pain, a stunning visual aid to showcase a wrestler's suffering. A wrestling match is designed to make the audience believe, believe in the wrestlers' motivation, emotions and pain. Blood pouring from one's head is something that forces fans to believe.
It makes a hero a victim, the victor a survivor. It is perceptible proof that a villain is getting what he deserves. It's the wake a monster leaves behind and the ruins of an allegiance torn apart.
Blood has a language all its own; it tells its own stories.
The Story of Hatred
When a wrestling rivalry gets personal, when it reaches maximum intensity, blood makes hatred more obvious, more visible and more moving.
Flash back to a match like Sgt. Slaughter vs. Pat Patterson in 1981. Those performers created a sense of palpable hatred before they even locked up. They brawled, they choked each other and their match would have been compelling as is, but blood pushed it further.
For their battle to end with Slaughter so drenched with his own blood, it spoke to the extreme level of hatred that this feud had reached.
When Shawn Michaels and Triple H's friendship dissolved, it was blood that helped show fans just how bad things had gotten between those two. Their match at the 2004 Royal Rumble used blood masterfully.
It became their medium to convey how enraged and desperate they were that night.
This is a story blood has helped WWE stars tell again and again.
Undertaker's bloody beatdown on Vince McMahon at Survivor Series 2003, JBL and John Cena's I Quit match at Judgment Day 2005 and Dusty Rhodes' violent matches with "Superstar" Billy Graham in Madison Square Garden in 1978 are among countless examples of hatred being underscored by blood.
The Story of Survival
A wobbly wrestler holds his hand up in victory after being held in chokeholds, being slammed to the ground and kicked in the head. The victor's sweat and pained body language can tell a story of that wrestler's resiliency and grit, but blood goes further.
It adds to one's aura of toughness.
Fans can dismiss clotheslines and DDTs as fake, but seeing a man's brow painted red is undeniable proof of how brutal a battle was, of a warrior's strength.
This shot of Steve Austin refusing to submit to Bret Hart's Sharpshooter at WrestleMania 13 was made far more dramatic by the fact that Austin's bald head was covered in blood.
He did a fantastic job of screaming and squirming to sell how painful the hold was, but watching him refuse to give in despite his blood loss helped launch his career. Blood elevated that story and Austin's reputation as well.
Randy Orton proved a lot to WWE fans by managing to take all of Mick Foley's viciousness and keep going. Blood helped make their Backlash 2004 match a classic as it became a more powerful story of a cocky up-and-comer surviving the onslaught of a sadistic veteran.
The same is true for the aforementioned Cena and Lesnar match at Extreme Rules 2012. The blood oozing out of Cena's head made his comeback that much more impressive.
Bloodshed makes the hero look more heroic for having fought through it. It makes the match more akin to a war, a victory more akin to survival.
The Story of Brutality
Men like The Sheik, Bruiser Brody and Abdullah the Butcher spent their careers torturing their foes, slicing open their heads with weapons and leaving their mark on their foes' flesh.
Blood helped sell their beastliness. It became the macabre aftermath of challenging one of these fearsome men.
A wrestler's size, demeanor and in-ring style can certainly help build a frightening reputation, but blood does it like nothing else can. To leave the canvas darkened with blood, to leave an opponent in need of stitches does wonders for one's reputation.
How much more animalistic did Lesnar seem after leaving Zach Gowen a bloody mess? How much more scary did a confrontation with Foley seem after it left one with lacerations?
Blood helped make Brody, Abdullah, The Sheik and many like them into monsters.
Blood in wrestling is something that appeals to the audience's dark side, much like the days of the gladiator. It's not for everyone, but WWE, like the circus, offers variety in its spectacle.
A single WWE event offers comedy, mat wrestling, acrobatics, soap-opera storylines, brawling and sometimes a departure into the darkness.
Blood is the equivalent of the circus freak lurking in the tent. As disturbing as it is, it's hard to resist peeking inside the tent to see it.
Years ago, an event like Extreme Rules would have been a guarantee for bloodshed. Today, it's a rarely used option and no matter how much WWE tries to wipe it away or hide it with black and white film, blood's power is undeniable.