Whether you're rolling a natural 20 in Dungeons & Dragons or a half-dozen 10's in Vampire: the Masquerade, the critical success is a big part of the game.

Every gamer knows the thrill of scoring a critical success. Whether you're rolling a natural 20 in Dungeons & Dragons or a half-dozen 10's in Vampire: the Masquerade, the critical success is a big part of the game. A critical success on a skill check can mean that a character dramatically succeeds on a seemingly impossible task, while a critical hit in combat can be the deciding factor in taking down an apparently invulnerable foe. In the most well-known fantasy games, many magical effects require a natural 20 to be rolled in combat, the most famous being the Lewis Carroll-inspired vorpal sword. Seeing that 20 come up on a die at pivotal moment is a rush, and although to my knowledge nobody has ever demonstrated this in a lab, I'm prepared to wager that in our brains, you probably get much the same surge in dopamine from a well-timed 20 that you do from, say, getting a jackpot on a slot machine.

For all that we live and die by our dice, a lot of game publishers don't put much thought into the flavour text of critical hits. Not too long ago, Paizo released their wonderful critical hit deck, which adds complex random consequences to successful critical strikes; instead of simply taking double damage, the victim may be disarmed, knocked prone, or even randomly transported to another plane. Even this deck, though, focuses primarily on the game effects of the critical hit and at best only hints at, for example, where the blow actually landed to have its effect. Although most parts of the body are sensitive and breakable, relatively few might have enough vulnerability to justify double of triple damage from hitting them. We all know that the savvy dirty fighter goes for soft targets like the eyes, the naughty bits, and certain key tendons, but here are a couple of less readily thought of but particularly interesting body parts which we might imagine are common sites of critical damage.

Given the opportunity to take out more obviously tempting targets, it might be expected for a combatant not to bother targeting the elbow, but there's a superficial structure which can make for a nice target of opportunity: the ulnar nerve, more popularly known as the "funny bone." The ulnar nerve is a major nerve that runs along the arm from just above the elbow to the little finger. Unlike the vast majority of the body's nerves, the ulnar nerve runs for a significant distance with very little protection; in the area where it runs alongside the far end of the arm bone (the "medial epicondyle of the humerus"), the only thing covering it is a tough layer of skin, which lacks the shock-absorbing power of muscle. When something hits this nerve, usually an impact from behind or below, it triggers what most people will describe as a shocky, electrical-like pain, which can be accompanied by numbness of part of the hand and difficulty flexing a couple of fingers. Funny bone pain doesn't tend to last terribly long, so it may not seem like it would be severe enough to constitute hit point damage, but a strike to the ulnar nerve has narrative use. Most of our players have never suffered a major stab wound, or been engulfed by fire, or been level-drained, and it's hard for players to imagine what those might feel like and the effect they would have on a character. In contrast, odds are good that every single player in your game knows how it feels to smash their funny bone. What's more, although the brain protects us by making it very hard for most people to remember exactly what a certain pain felt like, people tend to be able to very vividly imagine the feeling of hitting their funny bone. It's easy for a storyteller to describe without needing the use a lot of either vague or flowery description, and it'll elicit a wince from a good number of your players, to say nothing of their characters.

Another often overlooked site of critical hits is the spleen. I've often thought about this, and it seems to me that the best explanation for this is that, while a lot of people know the word "spleen" and know that it refers to a fairly squishy and delicate part of the body, not a lot of people know what, exactly, the spleen is, or where you would have to be hit to damage it. The spleen is a rounded organ, slightly smaller than a clenched fist, found in the upper left part of the abdomen, pretty much up against the back muscles. By virtue of its position, it tends to be reasonably well-protected by the ribs behind and on the side and by the kidney and guts in front. In an ordinary, healthy adult human, the spleen is extremely difficult to feel on examination of the body, and physicians tend to have to perform all sorts of specific movements and maneuvers to feel for it unless it's enlarged (which happens in a lot of different diseases). In spite of its protected position, the spleen is a fairly delicate, pulpy sort of thing that can be bruised or ruptured by abdominal trauma. Certain diseases and infections can make the spleen grow and become particularly delicate, and if you've ever had infectious mono, you were probably advised not to, say, play football for a few weeks. A big part of the spleen's function has to do with storing some of the body's blood supply, so when the spleen is damaged, it can lead to rapid and severe internal bleeding. Presumably, a little splenic laceration or rupture gets fixed up by your basic Cure spells, but a splenic injury could go a long way to explaining why your took so much damage from the same club that barely scratched you the prior round. Of course, the area where the spleen is found would generally be among the best-armoured parts on a warrior's body, so splenic injury probably isn't the most common war injury seen by healers, but it's certainly a common enough injury seen in modern emergency departments and military casualties.

More than four years ago, Dr. Eris Lis, M.D., began writing a series of brilliant and informative posts on RPGs through the eyes of a medical professional, and this is the one that appeared here on October 27, 2013. Lis is a physician, gamer, and author of the Skirmisher Publishing LLC OGL sourcebook Insults & Injuries, which is also available for the Pathfinder RPG system.