Stronger with Age

""I kill where I wish and none dare resist. I laid low the warriors of old and their like is not in the world today. Then I was but young and tender. Now I am old and strong, strong, strong, Thief in the Shadows!""

- Smaug, the dragon, The Hobbit

Everyone knows a child is more durable than a newborn, and that an adult is tougher then a kid. However, for some creatures this keeps going with age. They never grow decrepit. Arthritis never settles in. They keep growing stronger, faster and more resilient with each passing year. What is to note is that the older creatures are not simply more powerful due to having more experience: they are literally tougher than any younger specimen of the same breed.

Vampires and Dragons are two of the most common species to exhibit this, with ancient Dragons and elder Vampires possessing terrible power. This can cause a bit of Fridge Logic if the creature is stated not to be immortal: if dragons become more resilient as they age, then just how do they die of old age?

A subtrope of Older Is Better. See also Monster Lords, who are often older members of their species, and contrast Evil Makes You Monstrous (for the latter, they get eviler with age and thus get uglier and stronger). For the human equivalent, see the Old Master and Badass Grandpa. See also Monster Progenitor and Mother of a Thousand Young.

Anime and Manga

 * In an early episode of Yu-Gi-Oh!, Joey/Jonouchi defeats an opponent by allowing his Baby Dragon to age a millennium into the much-more-powerful Thousand Dragon.
 * It's also true with Yugi's Dark/Black Magician, who becomes the Dark/Black Robed Sage after also having a thousand years to study the arts of magic.
 * The Lyrical Nanoha franchise has Voltaire, an ancient black dragon so powerful, it's practically revered as a Physical God in Caro's home planet of Alzus, with Caro serving as a priestess that it occassionally lends its power to. In contrast, Friedrich, the young dragon that Caro raised on her own, is mainly used for support fire and transport even in his full form.
 * The Saiyans in Dragon Ball. In Dragon Ball Kai Doctor Gero thinks this shouldn't happen, and that any powerup Goku got after the Saiyan saga would be negated by his age. He's immediately proven wrong when Goku goes Super Saiyan.

Comics

 * In Kingdom Come Superman is said to be undergoing this. After so many years under Earth's yellow sun, he's stronger than ever, and immune to Kryptonite.
 * Grant Morrison's Superman gets more powerful over the next 80 millenia and eventually bestows powers on his descendants.
 * The Maestro, the future version of the Incredible Hulk, who is stronger and smarter than present day Hulk (even when PDH is in smart mode).
 * Part of the rationale is that there had been a nuclear war, and since the Hulk is radiation-powered, this made him stronger at the expense of his sanity (well, at the expense of Smart Hulk's sanity).

Film

 * Anacondas: Hunt for the Blood Orchid uses this to justify Attack of the Fifty Foot Whatever: the titular snakes are stated to keep growing for their entire life, thus ones that consume blood orchids--flowers that can prevent aging--can grow to be much bigger than normal.
 * The vampire Elders in Underworld are stronger than any other vampire and, in some cases, can even defeat lycans in hand-to-hand combat. In a memorable example, Viktor grabs Raze in his lycan form by the throat, holds him up for a few seconds, and then breaks his neck. In the case of Marcus and William, the Corvinus twins and progenitors of the vampires and lycans, respectively, they are also stronger, although this can be attributed to Monster Progenitor. In Marcus's case, his strength is augmented tenfold after he accidentally ingests lycan blood and becomes a hybrid. William was already stronger than any other lycan. According to Selene in Underworld: Evolution, Alexander Corvinus, the original immortal and the father of the twins, is easily the strongest of them all, although he refuses to fight or otherwise make use of it.

Literature

 * Dragons in JRR Tolkien's writings do this. Smaug provides the page quote.
 * So do Elves. The more they age, the wiser and more powerful they are. Being immortal helps.
 * The Silmarillion mentions that Elves might grow old if they reach a million years, but this might be speculation, and in any case the world in the setting is not yet that old. Círdan, the oldest Elf in Middle-Earth, has white hair by the end of The Lord Of the Rings, but whether his age has truly weakened him is not shown.
 * The undead in The Dresden Files universe grow stronger the older the remains that went into their reanimation are. This culminates with Harry using a Tyrannosaurus' skeleton to turn into a zombie.
 * The Dresden Files also plays with this trope concerning Black Court Vampires. On the one hand, it is noted that since Mavra is such an old vampire she is likely to be mobile and capable of defending herself during the day where younger vamps would be forced to sleep. But then they toy with it by pointing out that the reason Black Court vamps in general are such major Badass types is because of basic survival of the fittest since Dracula was published. To get to be that old, they have to have been Badass to begin with, or they'd have been killed (again) years ago.
 * The from Harry Potter and The Chamber of Secrets is apparently still in top form at the age of one thousand. And if the shed skins are any sign, she's still growing.
 * Dragons in The Inheritance Cycle never stop growing, some were as big as mountains.
 * The vampires in Anne Rice's The Vampire Chronicles books get stronger as they age. Even after doing nothing but sleeping for hundreds of years, they wake up stronger than they were before. Drinking the blood of an older, more powerful vampire can also add to their power.
 * They also obtain new abilities with age, or "gifts" as they call them, the most common one being the Cloud Gift which enables flight. Interestingly, no vampire is ever comfortable with flying, realizing how unnatural it is (even for a vampire), except for Akasha and Lestat (who gained these abilities after drinking her blood).
 * Eventually subverted in Mikhail Akhmanov's Arrivals From the Dark series, where the Dromi continue growing as they age, which initially does make them stronger with age. However, as they reach about 500-600 years old, the Square-Cube Law takes into effect, making it very difficult to move, and they eventually get crushed by their own weight.
 * The vampires in Barbara Hambly's Those Who Hunt the Night and sequels grow tougher as they age, eventually becoming resistant to their weaknesses - an ancient vampire such as can withstand the touch of silver that would burn and sicken a fledgling (newly created vampire) with even the slightest contact and even resist the light of the sun and the irresistible sleep that forces all younger vampires into a coma during the daytime hours. Their psychic powers (and presumably physical strength) also increase with age, although there are also possible, though inconsistant, degredations with age (the Bey of Constantinople, for example, ).
 * In the Wiz Biz series by Rick Cook, dragons grow larger and more powerful with age, and have no known natural upper limit to their lifespans.
 * The Nobility in the Vampire Hunter D universe are also like this; and since the series takes place in the far future circa 12000 AD, where most of the time between now and then was dominated by vampiric rule following a nuclear armageddon Twenty Minutes Into the Future, some are very old indeed. Somewhat subverted in that a recent human uprising wiped out most vampires, and that those remaining, for all their terrible power, are a dying race. One of the recurring themes of the novel is that while humans are, on the whole, weak, short-lived, and otherwise flawed, vampires have an even greater, fundamental flaw which dooms them to eventual extinction; as the Revered Ancestor once put it when speaking about his kind, "Transient guests are we."
 * Trolls in Discworld are theoretically immortal, but as they get older they get bigger and slower and tend to be more inclined to sit and think. They call this "getting philosophy". Eventually they just stop moving altogether, gradually "decomposing" or eroding into an oddly shaped heap of minerals with a tiny living spark in the center. Many of the Discworld's mountains are actually very old trolls. I suppose this only fits if you consider mountains to be powerful...
 * Shown to be true when a troll warns a character about his grandfather, who is one of the mountains and is very annoyed when some adventurers light a campfire in his mouth.
 * Darklings from the Midnighters series grow much, much stronger with age. Of course, they also get crazier with age.

Live Action Television

 * Vampires work this way on Buffy the Vampire Slayer. Older vampires become stronger, tougher, and more demonic in appearance, and may pick up other powers, like Dracula's tricks. When Spike is first introduced Giles initially dismisses him as a big threat when he discovers Spike is scarcely over 100 years old (shortly after he discovers Spike's full history and reconsiders). Kakistos was noted as being an extremely old vampire and thus a bigger threat. His age meant he had lost most traces of a human appearance and a standard size stake wouldn't do the job, so The Master was another vampire old enough to have stopped looking human, and had somehow gained the power to open the Hellmouth.
 * Rather casually subverted however in the spin-off Angel, in which the title character in a flashback meets an incredibly old vampire known only as the Prince of Lies, who despite his markedly inhuman appearance is killed as easily as any other vampire.
 * In Moonlight, Mick senses (or rather smells) that Lance is very old, who further reinforces this by jumping from a tall building (impressing even Mick) and surviving being burned (any part of a vampire that touches fire is normally instantly turned to ash).
 * Coraline also somehow survived being trapped in a burning building and could move with a stake in her chest, which is normally impossible.
 * By contrast, the 700-year-old Lola was pretty handily defeated by Mick, despite being able to move much faster than him.
 * In The Vampire Diaries vampires all become stronger as they age, although the difference can be overcome through numbers, surprise, anti-vampire weaponry, or other tactics. The oldest of them, the Originals, get a whole bunch of nifty powers and are next to impossible to kill. When they did manage to take one down, he would only remain dead as long as the magical knife that killed him wasn't removed, and his body remained indestructible.
 * Vampires from True Blood. They gain more and more abilities as they age, older ones having more and more celerity, and some of the oldest ones have developed the ability to fly. This works both ways, however: a 2,000 year old vampire will burn up in the sun within seconds, whereas a younger vampire will take minutes.
 * Apparently, even younger vampires have limited flight capabilities. They just don't do it often. Bill (who's not even 200) was able to lift up a few feet off the ground and lunge forward when he fought.
 * The Old Ones from Being Human. While they still can be killed as easily as any other Vampire, they have a lot more "tricks" under their belt, with some such as Wyndham being able to casually enter without an invitation, something that would cause most Vampires to instantly begin to boil alive.
 * Some physiological changes seem to occur with age as well. Mr Snow, the leader of the Old Ones, has developed a sickly pallour, rotting teeth and protuding black veins due to his advanced age.
 * Ghosts are also stated to get stronger with age. Most however fail to get that far due to losing their connection to the mortal world, leading them to simply fade away into non-existance.

Religion And Myths

 * In Japanese folk thought, foxes (Kitsune) grow a new tail for every hundred years they live, with a proportional growth in power, to a maximum of nine, at which point they're pretty much Physical Gods.
 * In fact, there's a whole subgroup of Youkai/Obake who were former ordinary objects or animals who acquired supernatural powers and sentience after being used/living long enough (usually about a century).

Tabletop Games

 * Dungeons and Dragons has this happen to many creatures. Vampires, dragons, liches and others tend to grow more powerful as they age. Pictured above are red dragons. For the record, the second largest one is an "adult". The top one is an ancient.
 * The "Draconomicon" sourcebook partially subverts it by introducing a bit of mostly-fluff about most dragons progressively weakening and becoming senile after a few millenia; however, this is relatively easy to remedy for any dragon with the motivation to do so.
 * The Ravenloft setting is especially keen on doing this with The Undead, being a Gothic Horror setting. Vampires, liches and mummies especially get age categories similar to those of dragons.
 * Warhammer and Warhammer 40000 contains plenty of examples, and though many are due to the "more experience" version many others fit this trope. Orcs/Orks, for example, grow larger, tougher and meaner with age, the oldest being hulking monstrosities even by their standards. A more minor example, SpaceMarines seem to grow in size along with rank and age. It is theorized they practically never stop growing, though it will lessen.
 * Less noticeably, although dwarves do not get larger with age they do get notably tougher until they are near death.
 * In the Munchkin card game, "Ancient" is a +10 monster buff.
 * The RPG adaptation of Munchkin inverts this for the plutonium dragon, which becomes weaker every 24,100 years (the half-life of Pu-239).
 * The World of Darkness
 * Vampires in the Old World of Darkness game Vampire: The Masquerade are stronger with age in two ways: experience and Generation. Older vampires are more experienced (obviously), have more and stronger Disciplines than neonates, and have influence over vampiric and human society. A vampire of lower Generation is closer to the blood of Caine than a 13th-Generation neonate (the game's "default" new player characters), increasing their stat caps and allowing them to spend more Vitae faster.
 * The successor game, Vampire: The Requiem, subverts this with its Blood Potency stat. Like Generation, higher ranks of Blood Potency allow a vampire to spend more Vitae and have higher stats, but can't regain Vitae from animals and eventually humans. Instead of being a simple "I'm stronger than you" score, high Blood Potency invokes a psychological need to enter torpor, during which the vampire's Blood Potency drops and he forgets his experiences (the so-called "Fog of Ages"). Ergo, no Kindred stays stronger with age, since they depower while in torpor and their memories become faded dreams. Methuselahs, however, do not suffer the Fog of Ages.
 * In a fantasy-steampunk RPG Wolsung, trolls fall under this trope without exceptions. When they are about 50 years old, they start to burn out mentally, fall into fits of rage, and at some point they hulk out. Permanently. From this point, they become larger, more resilient and feral with age... and nobody ever checked just how old they can get. Usually, their family or the authorities will put them down shortly after the onset of this freakish senility.
 * It's less pronounced with troll women, who don't lose so much of their brains - just their morals. They are more likely to serve you arsenic tea and cyanide cookies than to rip you limb from limb. At least in the first stages of senility. Then they get worse.
 * This "old troll syndrome" is the reason why most well-mannered trolls are expected to commit suicide when they notice the first signs of old age, to prevent a scandal (Victorian morality in practice). Those who are unable to perform the act usually depend on their next of kin to assist them once the transformation starts.
 * The potential for power of Exalted is tied directly to age, with caps placed on their highest potential Essence based on how long they've lived (although there are a few magics that can break this). The highest levels of power are only available to Exalted who are more than a thousand years old.
 * One scenario in Betrayal At House On the Hill reveals the house to be alive and capable of draining the inhabitants' life, making them age rapidly. (With the exception of the Traitor, who brings victims to the house in return for eternal youth.) Character stats start dropping rapidly once a certain age is reached, but the youngest characters actually get a stat boost for a while as they become grownups.

Video Games

 * Fallout 3 Super Mutants grow stronger with age. Super Mutant Brutes are younger and weaker than Masters, who are weaker than Overlords, who are weaker than Behemoths, who are the oldest. Not that this particular trait is not (explicitly) shared with their west coast counterparts.
 * In fact, in Fallout 2 the Super Mutants of Broken Hills are said to be slowly going weak and senile. This is probably due to being infected with a different strain of FEV (found in the Mariposa Military Base) than the mutants in the Capital Wasteland.
 * The asari in Mass Effect are said to show this, at least with regards to their biotics, which grow in power as they reach the matriarch part of their life cycle.
 * Dragons in Dragon Age only get more powerful with age. The Darkspawn also demonstrate the same is true of them, with a mini-boss Hurlock Vanguard in the Deep Roads called "Ancient Darkspawn."
 * And then, in Dragon Age 2 Legacy, there's, the most ancient Darkspawn (or at least, one out of half a dozen of them).
 * The same could be said of the Grey Wardens, due to the Darkspawn Taint within them getting stronger over time. However
 * Some of the monsters in Dark Sector are stated as getting larger and stronger with age. Just before a boss fight, an ally warns you, "This one is very old!"
 * Vampires in The Elder Scrolls grow more powerful as they age. Vampire Ancients are the oldest and strongest.
 * While many Touhou characters are powerful due to winning the Superpower Lottery, many more obtained it seemingly by virtue of being around for so long. 500 year old Remilia is almost as powerful as her sister Flandre, despite the latter possessing the second biggest Story Breaker Power in the setting. Kanako and Suwako are more than 2300 years old and with power worthy of their station, despite the years with barely any faith to sustain them. Yuuka is noted as one of the oldest living youkai, as well as one of the strongest, despite her explicit ability being controlling plants. Eirin is a Time Abyss and quite possibly only surpassed in power by Yukari, with even the Watasuki sisters respectful towards her. And Fujiwara No Mokou is a human who is now EX-Boss strength, due solely to the immense amount of time she has to practice.
 * Additionally, Ran Yakumo is a Kitsune and Chen is a Nekomata. Both are Youkai who were originally animals, but grew stronger with centuries of age.
 * Woses in Battle for Wesnoth. Elder and Ancient Woses are stronger than normal ones and sapling.
 * Nym, from the Star Wars Starfighter series, is a Feeorin, who are specifically noted to grow progressively stronger as they age. And since they can live as long as four hundred years, that's quite a lot of room for growth.
 * Liir from Sword of the Stars have this; the older they grow, the larger they get and the more powerful their psionic abilities become. The only thing limiting their size, and eventually causing their death, is the Square-Cube Law.
 * Dragons in Castle of the Winds, with "Ancient" ones the strongest of all.
 * Legacy of Kain: Vampires "evolve" over time, occasionally entering a cocoon-like state and emerging changed; Typically stronger and with new abilities, as well as less human. But Kain's caused his descendents to eventually degenerate(or something similar). It's implied that a vampire's evolution conforms to his personality; Vorador's chin horns used to be a similar beard, human Rahab's armor had a sea horse painted on it, and Raziel told Zephon the latter's final form is a true representation of his soul. It's revealed in Soul Reaver 2 that some changes, like the typical three-fingered hands, are.
 * In Guilty Gear, Slayer is a Nightwalker who is several hundred years old, the original founder of the assassin's guild, and one of the most powerful characters in the series. It's heavily implied that he's holding back on the whole cast; even if you utterly destroy him in a fight, he'll just lie on the floor with his head in his hand, casually chilling out.
 * Also, Jam Kuradoberi, who is told after fighting Slayer that given enough time, she'll end up surpassing him.

Web Comics

 * Immortals from El Goonish Shive continue to get older, smarter, stronger, more bored and less sane until the point comes where they basically become Persons Of Mass Destruction. To prevent this, they voluntarily undergo a kind of ritualistic death/rebirth cycle every couple centuries to lose most of their power and memories so they can start over and keep things interesting. Not all of them do this though...

Western Animation

 * Mumm-Ra on Thunder Cats is the Big Bad partly because he's a thousand years old.

Real Life

 * Truth in Television: Gustave the Crocodile is over 66 years old, believed to be over twenty feet long and two thousand pounds heavy, and still killing people to this day.
 * Trees, sequoia in particular.
 * Lobsters are a perfect example. According to recent research, a lobster does not weaken or slow down with age. In fact, it becomes more fertile as it gets older compared to younger lobsters. Barring injury, disease and capture they can live on indefinitely, reaching impressive sizes. All this is attributed to telomerase, an enzyme that repairs DNA sequences of the form "TTAGGG". This sounds cool until you realise that theoretically, there could be centuries-old lobsters the size of houses scuttling around on the ocean floor. Or not, since they'd have to eat.
 * There's serious scientific research to allow us to do the same. The only problem is it's a double-edged sword. Telomeres wearing down puts an upper limit on cell multiplication, but trying to take away cellular regulatory systems can result in immortal cells that can multiply indefinitely but also grow out of control, turning into cancer.
 * Reptiles in general. Most animals reach a certain size and stop growing. So long as a reptile doesn't get killed or die by other means it just keeps getting bigger and bigger as it ages. Of course, they still die of old age at some point.
 * Sharks. It is believed that some great whites still swimming the seas today are centuries old.