A birthmark, scar, subcutaneous pigmentation, magical tattoo, or otherwise permanent/semi-permanent mark on a character that somehow ends up being significant to the plot BY A CHANGE IN IT or something unusual that it does; it can't just be static. Disappearance of the mark, the stoppage of its unusual function, or a discovery that the mark was never real is part of this trope. Normal healing of a wound to a scar does not count; a wound that does not heal due to magic or poison may, as long is it does more than just not heal (i.e., bleeds excessively when the inflicter of the wound is near, etc.). Subtrope of Distinguishing Mark. With examples, please include the noteworthy change in the mark.
See also Power Tattoo for marks that grant their bearers some abilities, Marked Change for ones that merely indicate the current status (like Super Mode) and Mark of the Beast for Evil Makeover variety.
- InuYasha: Miroku's Wind Tunnel functions as such. Once a year, it will expand and grow more powerful, until it breaches the confines of his palm and consumes him. It can also be damaged by outside sources like blades, which accelerates its growth even further.
- In Naruto Sasuke's Curse Seal acts as this immediately after being applied. When his will or chakra weaken enough, it spread across his skin like a rash, causing additional weakness and pain. It is later upgraded to allow him to draw on its power without the side effects.
- The curse mark on Alan in MÄR. If it goes all the way up his neck, he becomes a zombie slave.
- In Magical Record Lyrical Nanoha Force, the Blue Wings "tattoo" appears somewhere on the body of a person infected with Eclipse and grows larger as the infection progresses.
- Tomoe from Kamisama Kiss has them appear all over his body thanks to a Deal with the Devil.
- Oga from Beelzebub gets a red mark along his arm that shows his connection with Baby Beel. It is a plot point in early episodes that he must live a peaceful life to remove the mark and go back to his old life. It doesn't take.
- The burn-like curse left on Ashitaka's forearm by the corrupted boar god Nago in Princess Mononoke is what drives him to leave home and search for a cure before it spreads up his arm and kills him. As a beneficial side effect, it also grants him Super Strength. At the climax of the movie, the spread accelerates until it's visibly crawling across his body, and even spreading onto his love interest, San.
- Jack Sparrow's "Black Spot" in the Pirates of the Caribbean: Dead Man's Chest. It disappears and reappears as his debt to Jones is settled or still needs to be satisfied.
- Harry Potter's scar counts; not only is his scar an indication that he survived the Killing Curse, but it twinges whenever Voldemort is feeling something particularly strong. The connection to Voldemort becomes stronger as the series continues.
- The titular character's scar in Robin McKinley's book Sunshine. After Sunshine defeats the vampire who gave it to her, it disappears completely.
- In Azure Bonds the eponymous pseudo-tattoo, among other functions, linked Alias to her bosses via their symbols, and there was a reason behind one empty place in their pattern. These vanished one by one when those masters were removed from the scene permanently, and later a mark of the goddess looking after Alias appeared. So when in the third book an old symbol returned...
- Artek "the Knife" Ar'talen in Escape from Undermountain was given a magical tattoo after he was "employed" via set-up escape by a noble. It mirrored the sun and moon position in the sky and was set to release a killing spell at the pre-set time — as an incentive to complete his mission and return for removal before the deadline.
- In The Dresden Files, a Red Court vampire doesn't fully turn the moment they're infected, but the first time they kill through feeding; they can even use some vampire powers and drink blood to heal and "recharge" without losing their human selves and becoming evil. The Fellowship of St. Giles, a group of these half-vampires, have tattoos that help control their bloodlust. By default, they're invisible, turn black when the half-vampire's using their enhanced abilities and getting hungry, and bright red when those urges are getting out of their control.
- Vimes' scar in Thud!, which he gets from tearing his hand open on a rusty nail and gets eerily inflamed whenever Vimes get angry over some injustice. The scar turns out to be the entry point where the Summoning Dark came into his body, and after being burned by burning oil in same location the scar turns into a picture of the Summoning Dark.
- Fuses in The Candy Shop War. Unlike most engineered apprentices, who only have a single power, Fuses have a suite of abilities rivaling those of a true wizard. However, every time a Fuse uses their powers, the mark on their body grows to cover more of their skin. When it covers their entire body, they die.
- In an episode of Star Trek: Enterprise, Hoshi Sato is worried that the transporter altered her structural integrity on a molecular level. She cites a mole that moved an inch lower on her face after her transportation as proof. Oh, and she ends up being right.
- In Power Rangers Lightspeed Rescue, once Ryan the Titanium Ranger joins the good guys, Diabolico inflicts him with a snake tattoo; every time he morphs it'll climb up his back until it reaches his neck and kills him.
- Played for Comedy in NewsRadio. An impostor once performed an appendectomy on Max. When the imposter shows up at the station, Max proclaims the scar "knows he's near."
Max: The scar! I can still feel it throbbing!
- In Final Fantasy XIII, a l'Cie's brand changes in appearance to indicate how much time he/she has to complete his/her Focus before becoming a Cie'th. It gets arrows, and then a red eye, when the brand reaches the thirteenth stage and the eye is fully open the l'Cie becomes a Cie'th. Notably, emotional distress can accelerate the process, so much that the datalog notes that somebody can become a Cie'th immediately upon branding due to panic/shock/horror about being made l'Cie. Fang's brand is white and blurry, indicating that she's not on a timer. This happens to the brands on the rest of the cast at the end, and the brands disappear entirely after defeating the final boss.
- Ninja Gaiden 3: At the end of the first mission, Ryu is cursed with the Grip of Murder, which forces him to endure all the pain of those killed by his Dragon Sword, and will eventually kill him. It initially manifests as a literal Red Right Hand, but as the game progresses, it spreads until, by the final mission, it's covered his entire right arm, part of his face, and one eye.
- In Sonic and the Secret Rings, Sonic is scarred with an arrow of flame. It shrinks with his lifespan; the smaller the flame is, the less time he has to finish gathering MacGuffins. Right before the final boss, the camera has to zoom in for you to even see it. When Shahra Takes The Bullet, this thing gets subverted all the way to Jahannam; Darkspine Sonic has his flame on, and he is not scared of using it.
- In Prince of Persia: The Two Thrones, the Prince gains yellow glowing marks on his arm where the Chainwhip is embedded in his arm, and gains a Dark Prince persona. Over the course of the game, the corruption slowly spreads up his arm and into his shoulder.
- Used in the Dan Vs. episode "The Monster Under the Bed".
- Invoked in the short-lived children's series Sagwa, the Chinese Siamese Cat. In one episode, Sheegwa, Sagwa's younger sister, is discovered to have a star-shaped marking on her fur that is "the mark of the princess", indicating that Sheegwa is actually a princess. Unfortunately, the mark turns out to be dirt.
- In Trollhunters, when Angor Rot captures Jim, he marks his face with a magical mark that appears on Angor's command. This gives Angor the power to take Jim's Sword of Daylight during battle, forcing Jim to use alternatives. He eventually overrides this by using a gemstone housed within Angor's disembodied right-eye.
- When Moon Butterfly from Star vs. the Forces of Evil used Eclipsa's destruction spell to blast off Toffee's finger and frighten away his armies, blackened veins appear on her arms, forcing her to wear gloves the rest of the time. This grows steadily worse overtime, the process speeding up exponentially after Moon is overcome with grief and anger when she thinks Star dies. Eclipsa's hand is also dyed black, possibly due to her extensive practice in the dark arts.
- Skin cancer. If one of your Beauty Marks turns color, gets bigger, or otherwise starts looking wonky, see an oncologist pronto!
- And, of course, if any sort of wound doesn't heal the way it's supposed to (i.e., scab over with minimal scarring), it's probably infected.