Precursor Heroes

A hero or group of heroes (often oddly similar to your own Player Party) that arose in the hour of need and sealed the Ultimate Evil in its can 1,000 years ago. Often shows up in As Long As There Is Evil or similar scenario (like the aforementioned Sealed Evil in A Can) where the evil recurs. May be the sire of the hero's Heroic Lineage and original bearer of the Ancestral Weapon. Contrast Predecessor Villain.

Anime & Manga

 * In Digimon Adventure it's revealed that the heroes weren't the first group of digidestined.
 * In Digimon Frontier, Lucemon was sealed by a group of 10 ancient heroes.
 * One episode of Demashita Powerpuff Girls Z showed that there were analogues to the girls in the Edo period that sealed Him away in a volcano.
 * Heartcatch Pretty Cure establishes that there were many other Cures that had their own adventures long before the four main heroines did. Only two of their forerunners were actually shown (although others appeared in the form of anonymous statues) -- the heroine's grandmother, formerly known as Cure Flower, is a mentor to the team, while Cure Angie, who was active four hundred years ago and is stated to be the first Cure in history, briefly appears in the movie.
 * This doubles as a Mythology Gag, as there really were other Cures having adventures before the Heartcatch heroines.

Films -- Animation

 * The Beatles' animated Yellow Submarine has the original Sgt. Pepper's Lonely Hearts Club Band as Sealed Good in A Can. Probably suggested by the Sgt Pepper album cover where the waxwork Beatles in their mid-1960s suits are looking at the real ones in their Sgt Pepper outfits.

Live-Action TV

 * The earlier Seekers, such as Kieran, on Legend of the Seeker.
 * Several Power Rangers teams turn out to not be the first like them (though they would often be the first to use Ranger powers). Details about them tend to be left pretty vague, except in a few cases.
 * With the original Mighty Morphin Power Rangers, it's been hinted that Zordon has long been known to Recruit Teenagers With Attitude, though we never get more details than that.
 * In Power Rangers Wild Force one of the warriors from 3000 years ago turns out to have been posessed, and after exorcism, becomes the Sixth Ranger. Also, the Giraffe Zord was once the signature weapon of one of the others, and one of the later weapons is named after him. We don't get to know the previous team, but saw flashbacks: they used the Crystal Sabers and Wild Zords but did not have Ranger-like suits, resembling knights instead.
 * In Power Rangers Dino Thunder, the original Rangers could be considered the precursors, as The Mentor was Tommy and his old team got a few mentions.
 * In Power Rangers Mystic Force, most of the group from last time around are major characters, probably because in this case the seal only lasted twenty years rather than the usual thousands. One of last time's group is The Mentor, two are the Big Bad's dragons (one Brainwashed and Crazy, one a traitor), one was Sealed Badass in A Can and becomes the new Sixth Ranger, and the Sixth Ranger from last time is mentioned at least once as a Posthumous Character.
 * In Power Rangers Jungle Fury, there were seven Old Masters who sealed Dai Shi away millenia ago, and for the most part they're still around to serve as The Mentors to the current guardians. One gets hit with the Mentor Occupational Hazard in the first episode but visits a few more times as Spirit Advisor, three died in the battle to seal Dai Shi but the Rangers are able to visit the Spirit World to learn from them, and the last three make recurring appearances as Retired Badasses. The fact that the surviving Masters are several thousand years old is completely ignored. The final battle brings all seven together to join the young 'uns in kicking major ass.
 * In the intro to Power Rangers Samurai, it is shown that a group of Samurai from Feudal Japan originally sealed Master Xandred and the Nighloks into Sanzu River. Also a few years prior to the main series, the Rangers' parents fought the Nighloks before their generation's Red Ranger sealed Xandred again after he broke out (which is implied to be a common occurrence; no Red Ranger has been able to make the seal permanent). This is a rare instance to show the precursors as actual Rangers using the same suits.
 * On the Super Sentai side of things, the core 5 of Gosei Sentai Dairanger are distant descendants  of the five Dai Tribe warriors who originally fought the Gorma thousands of years ago. These original Dairangers were destroyed when the red one was seduced over to the Gorma side and led the others into a trap..
 * The previous 34 teams became precursor heroes in Kaizoku Sentai Gokaiger. They drove the Zangyack away from Earth by sacrificing their powers to create a huge explosion. The powers were eventually collected by AkaRed, Basco, and Marvelous, before being used by the Gokaiger team.

Video Games

 * Dragon Age II: The protagonist's father, Malcolm Hawke, who's heroism is explored in the game's Legacy Downloadable Content. He's dead before the start of the game, but due to his use of magic, we get to hear his Badass Baritone.
 * The Cooper family in Sly Cooper.
 * Most Fire Emblem games have them. Summarized on this fan site.
 * In Overlord it's given a twist; they're the antagonists who defeated your predecessor.
 * The Legend of Zelda the Wind Waker's Hero of Time (the main character of The Legend of Zelda Ocarina of Time).
 * And The Legend of Zelda Twilight Princess, where the Shade is also implied to have been a previous hero (again, confirmed to be Ocarina's).
 * In The Legend of Zelda the Minish Cap, "The Hero of Men" is mentioned in the legend at the beginning of the game.
 * In Tales of Symphonia, you have Mithos' party: . By the time the game actually takes place though, only Mithos is remembered at all, and not for what he actually did . Well, technically people remember, too...
 * In Tales of Phantasia, there's the original party that defeated Dhaos in the past: You end up going back in time and replacing these people.
 * In Paper Mario the Thousand Year Door, a group of heroes sealed the Shadow Queen behind the titular door a thousand years before the events of the game. They are implied to being cursed into the beings that are trapped in blacks chests, and who curse you with new abilities using a loophole to help you.
 * Final Fantasy
 * Final Fantasy V has 12 heroes who defeated an ancient evil that was after the same power as the game's Big Bad.
 * Then the Four Warriors of Dawn, who sealed away the Big Bad after discovering he was immortal.
 * The Reveal of Final Fantasy I subverts this trope:.
 * Auron, Braska and Jecht in Final Fantasy X.
 * Final Fantasy III reveals that legendary warriors tend to appear whenever the balance of light and darkness go too far out of alignment. Last time around it was the warriors of darkness out to stop the forces of light from going out of control and destroying the world.
 * In Lufia and The Fortress of Doom, you begin the game actually playing as the Precursor Heroes, as they defeat the evil Sinistrals; after that battle, you start playing as their descendants, who have to stop them from being resurrected. And then there's the Prequel, Lufia II Rise of the Sinistrals, which tells the entire story of the Precursor Heroes from the first game.
 * Terra, Aqua and Ven from Kingdom Hearts Birth By Sleep are the precursors to Sora and Riku in the Kingdom Hearts series. They were who Xigbar was referring when he told Sora that "he wasn't half the hero the others were."
 * Lunar the Silver Star has the Four Heroes -- Dragonmaster Dyne, Hell Mel, Lemia and Ghaleon, four warriors who fought to protect the goddess Althena against the Vile Tribe's hordes. During the course of the game, it is eventually discovered that
 * The Fable I game references plenty, particularly the Archon, who was the player character's uber-heroic ancestor. In turn, the player character serves as a Precursor Hero to his descendant, who is the main character of Fable II. In turn, the PC is the parent of Fable III's player character.
 * The Council of the Nine in Lusternia. They were the Vernal Gods who originally sealed away the five great Soulless Gods. They stand sentinel today as Avechna the Avenger, and are periodically reawoken if a Soulless manages to seep out of its prison.
 * The four Nord heroes who originally sealed Alduin away in The Elder Scrolls V Skyrim.

Web Comics

 * The Order of the Scribble from Order of the Stick.
 * Homestuck has a whole chain of these. The pre-Scratch trolls reset reality, thereby becoming Precursor Heroes to the post-scratch trolls both in and out of Paradox Space. The trolls themselves become Precursor Heroes to the kids by creating their reality... who they then team up with, because Paradox Space is Exactly What It Says On the Tin. The kids then reset reality, becoming precursor heroes to a new set of kids.

Western Animation

 * The Powerpuff Girls
 * One episode began in prehistoric times, depicting a trio of Powerpuff Cavegirls who accidentally sealed the bad guy and his mammoth in ice until he was thawed out in the present day. There was a prehistoric Mayor as well.
 * And should we forget the Steampuff Girls, who battled the Mojo Kid in the Old West?
 * Scooby Doo Mystery Incorporated reveals that another group of teens called Mystery Inc. existed before Scooby and the gang, until they mysteriously vanished. Fred likes the name enough to adopt it, and the main plot of the series is finding out what happened to them. As of this writing, we only know what happened to their Team Pet, Professor Pericles. He's...changed.
 * We now know.

Board Games

 * The Board Game Heroquest gives the names of the 4 heroes who defeated the villain Zargon years ago, and specifically states that the players are trying to live up to the example.