Over the course of it's long life span the Castlevania series has taken some very strange narrative pathways, although arguably nothing was weirder than when time travel was introduced into the series. Although an attempt was made way back on the Dreamcast, with Castlevania: Resurrection, that game was canceled and time travel wasn't brought in just then. No, it was take another few years before series manager, IGA, decided that what the series really needed was time travel.
Specifically the implication was that there was a corps or people who went up and down the timeline maintaining order, attempting to ensure that time ran its proper course. These "time agents" showed up twice in the series with their first appearance in Castlevania: Curse of Darkness. There, a mysterious man, Saint Germain, with strange powers and abilities, as well as knowledge of the future, stands in the path of the heroes, Hector. Why? What was his plan? What was it all building to?
Well, that remains unclear. The next time we saw a time agent it was Aeon and he was working in the very far future of Judgment. Clearly there was some purpose to their madness, some need to save the world from those who would seek to destroy it, but, again, little explanation for who they were or what they were really planning, long term, was ever discussed. But hey, the time agents sure were snappy dressers, eh?
Castlevania: Curse of Darkness
Appearing mysterious early in Hector's quest to find, and kill, the evil Issac, Saint Germain gets in the way of the hero, attempting to warn him off. There are any number of ways to view his interference: maybe he foresaw a future where Hector became a mindless host for the power of Dracula (something Issac was, indeed, plotting). Or maybe there were bigger plans for Hector that involved him avoiding his quest for revenge entirely. Whatever the case, Saint Germain kept it cryptic. After fighting Zead (aka Death), revealing his powers to manipulate time, Saint Germain disappeared with promises of his return.
And return he did, much later in Hector's quest, after the time traveler had been captured by Zead. When once again confronted with Hector, Saint Germain tried to stop the hero from moving forward (one way or another, for the sake of the timeline). When Hector seems adamant in his intentions, Saint Germain challenges him to a fight. Hector, though, wins the fight and Saint Germain finally acknowledges that Hector must follow his path, one way or another. Then the time traveler disappears once more, allowing Hector to move forward to his inevitable fight with Issac.
Saint Germain appears one more time, at the end of Curse of Darkness. This time he doesn't address Hector but, instead, turns to the player and talks directly to them (making him the only character to truly break the fourth wall in the Castlevania series). Here he talks about fate and destiny, acknowledging events like Dracula's eventual death in 1999 AD, cementing the fact that he's a time traveler. Then he fades away, never to be seen again.
Castlevania Netflix History:
A different version of Saint Germain shows up for the third season of the Netflix Castlevania series. Here he's an older man, beaten down by events in his life. He's spending time in Lindenfeld (the town Trevor Belmont and Sypha Belnades arrive at, kicking off much of their adventure in the season), studying the books and works of art at the local priory. This is a religious building, it should be noted, that had been taken over by evil monks, led by Prior Sala, who had, months before, forsaken God and had begun worshiping a hulking Night Creature that had stumbled into the city.
After a chance encounter with both Trevor and Sypha, Saint Germain explained why he was in Lindenfeld, and it wasn't just to study books. He'd been using a magical artifact he'd picked up before, one with a connection to a magic inter-dimensional place called the Infinite Corridor. He'd had a lover who had gotten lost in the corridor and he was desperate to get her back. As he followed that device he'd been led to Lindenfeld and, he suspected, another portal to the corridor was going to open under the priory. He feared what the monks could do if they somehow managed to open that portal.
His fears were more or less confirmed when he managed to sneak into the crypts under the priory and he found the hulking Night Creature, the Visitor, trussed up on a cross with alchemical symbols (in blood) smeared in front of it. He immediately ran to the town leader, the Judge to inform them, and they called in Trevor and Sypha as well. A plan was hatched to stop the monks from casting their spell as soon as possible.
Sadly, before they could act, the monks enacted their plan. They performed a ceremony that burned all the townspeople (saving those heroes that were already stalking up to the priory), sending their souls into the waiting maw of the Visitor. This gave the creature the power it needed to open the gateway and the beasts of Hell came pouring out. Trevor, Sypha, and Saint Germain went into the priory, with Trevor and Sypha fighting while Saint Germain (who was not a warrior) was protected by a shield of ice, following behind.
When they got into the crypts, Trevor and Sypha continued fighting the dread beasts while Saint Germain went to work on the portal. He kept it from opening further, but it was Trevor defeating the Visitor that allowed the portal to close. Before it was fully closed he leapt into the portal to go in search of his lady fare, with promises that he'd see the heroes again, one day.
By the time of the fourth season Saint Germain had gotten pretty desperate to reach his lost love in the Infinite Corridor. Unfortunately for him, each time he reached a room she'd once been in his lover had already fled again, off deeper into the dimensions of infinity. Finding the last place he'd ever seen her, a library stretching off into the unknowable heavens, the magician was confronted by a mysterious woman, the Alchemist, who told Saint Germain that his love was far out of his reach, off in dimensions he'd never get to if he didn't gather more power. To reach her Saint Germain would have to throw off all the shackles that limited him, things like "ethics" and "morality", and delve into the truly dark arts. Only then, with some guidance, could he truly master the powers that would reuinite him with his lost love.
Resolving to do just that, Saint Germain left the corridor and began his new, darker studies. Over time his groing power caught the attention of a vampire, Varney, who wanted to use this new font of dark magic for his own plans. He desired to resurrect Dracula, to bring the Dark Lord back to the Earth to continue his reign of terror. For his part Saint Germain was amenable as the process of resurrection would also greatly increase his own powers, proving he was ready to break through the corridor so he could find his lost love. Designing a plan to resurrect Dracula, along with Dracula's wife Lisa, merging their two soulds into a single body, a rebis, this combined monstrosity would have all the power Sant Germain needed and all the carnage Varney craved.
In contact with Varney, along with the Devil Forgemaster Hector (who provided Saint Germain with the spells needed), the magician set to work gathering what was needed. Varney gathered together Dracula's minions and set them to the town of Danesti to cause trouble and raise hell. This chaos attracted the attention of Alucard, as it was meant to, and the vampire knight charged to the town to defend its people from the Night Creatures. Once Alucard saw the carnage there, and spoke to the town's leader, Greta, he agreed to take the townspeople back to his castle, the former castle of Dracula (where the Dark Lord died), as it was the safest place, he assumed, to protect them. Unfortunately this was all accordingly to plan.
Once the townspeople were at the castle, the Night Creatures struck, causing carnage and chaos. Many, many people died and their souls, their very essences, were freed from their bodies. Saint Germain had already seen this down once before, six weeks prior in the town of Lindenfeld, so he knew what would happen. Saint Germain floated into the room where Dracula died, put up a barrier spell, and started pulling these souls into his spell. The pour damned souls were the key he needed to unlock the gateway to Hell and pull out both Dracula and Lisa into to undead body that had been created, the rebis. He began his work as Alucard and Greta tried in vain to defend the people from the monsters.
Turning the tide, though, was the unexpected arrival of Trevor and Sypha. They'd been dealing with Varney in another town, Targoviste, and when he'd discovered the gateway he needed, a magical mirror that could transport him to Dracula's Castke, he used it and fled. The heroes followed through the mirror, landing near Alucard and Greta, giving their strength to the fiht and fending off the Night Creatures. They all then ran up to the castle ramparts, finding the dark ceremony that had already begun in the chamber where Dracula died. It was then that Varney revealed his true self: he was Death, the first and oldest vampire who fed on the lifeforce of all living things. He'd fooled Sant Germain into help him by promising that the dark powers would let the magician break into teh Infinite Corridor's deepest secrets. This was a lie, though, and he'd just needed the magician to make the rebis and pull Dracula's and Lisa's sould into it.
Why? Because Death knew that the two souls would be tormented by each other, trapped within that body and unable to escape. It would drive Dracula crazy and he would unleash unspeakable evil upon the world in that new form. All the deaths and destruction would feed Death, making him a fat and happy vampire. Horrified, Saint Germain tried to pull the spell back and mostly succeeded. The rebis, already screaming, was torn assunder, freeing the souls of Dracula and Lisa. Death, angered at the betrayal, lashed out, dealing Saint Germain a fatal blow. The resulting explosions of magic from all this blasted the walls off the room, leaving only Trevor, Death, and Saint Germain together on the floating remains.
As Saint Germain watched, the Belmont battled Death, devoted to killing this vampire and freeing the world from his evil once and for all. Death, though, was powerful and proved to be the toughest creature Trevor had ever fought. The only way to kill the demon, Trevor realized, was to sacrifice himself, killing both of them at once. He unleashe everything he had, going in for the fatal strike to eliminate the vampire. But Saint Germain realized what as happening, too, and he gave of his last magics to save Trevor, transporting the hunter away as the death blow was dealt. Death was defeated but Trevor was saved, placed far away so that he would survive another day.
Magic expended, Saint Germain's life gave out. With his final breath he apologized to his love for what he'd done, hoping there would be some forgiveness in the afterlife.
Like his video game counterpart, Saint Germain has some knowledge of future events (making comments about things like "toilet paper"), although he doesn't seem to be able to freely time travel the way the video game Saint Germain could. His knowledge, instead, comes from his journeys in the corridor and the places, and time periods, he's seen there.
Fighting Against Saint Germain:
Although you see Saint Germain battle Zead early in the game, there's only one official battle the player actually participates in, and this comes much later. In the fight, Saint Germain will teleport around, trying to slash at Hector from behind. Watch out because his sword slashes can sometimes cause the poison status effect, further damaging you. After he slashes, though, he'll take a pause so you can layer on some damage. He can also freeze time to try and get an attack in on you. And he can cause radial damage around him, forcing the player to jump and retreat to avoid damage. Once he reaches half health he'll start spamming his more annoying attacks, causing time to speed up which means Saint Germain can attack more often. He'll also summon a thorny vine that will craw along the ground and attack the player.
And then, obnoxiously, once defeated he'll reverse time, refilling his health bar once, and the fight will start again. At this point, on top of everything else, he can bring out a gun and shoot three times at you. He can really layer on the damage if you aren't careful. Thankfully, after three times through his health bar, Saint Germain will stop and you can continue your progress through the game.