Limited to snippets and flashback appearances in Harry Potter, this enigmatic and dangerous wizard remains something of a mystery to the casual Potter fan, known mainly as a predecessor of Voldemort who was at the height of his power during the first half of the 20th century. For better or for worse, we now know that Johnny Depp will be portraying the character but what can we expect from Depp’s Grindelwald going forward?

From his troubled school days to his rise to power, here are 15 Things You Didn't Know About Grindelwald.

15. He Made His First Appearance On The Back Of A Chocolate Frog Card

Grindelwald’s influence on the Harry Potter story doesn’t begin to become apparent until the back end of the series, but the notorious wizard actually gets his first mention in the Sorcerer’s Stone, used as a way of determining Dumbledore’s age and power at an early stage. After meeting the Weasleys and being coaxed through the apparently solid barrier between platforms nine and ten at King’s Cross, Harry boards the Hogwarts express and is introduced to Chocolate Frogs by Ron.

Every Chocolate Frog comes with a Famous Witches and Wizards card, each complete with a moving portrait and a short biography. These collectible cards depict some of the earliest practitioners of magic, from medieval Russian Hag Babayaga, who regularly ate children for breakfast, to ancient Greek witch Circe, infamous for turning lost sailors into pigs. There are some living wizards among the ranks, however, and Harry inevitably gets Dumbledore's card.

From the back of the Hogwarts heaster’s card we learn that Dumbledore is famous for his discovery of the twelves uses of Dragon Blood, his alchemy work with Sorcerer’s Stone creator Nicholas Flammel, and his legendary duel with Gellert Grindelwald. The card simply mentions that Grindelwald was considered a Dark Wizard who was defeated in 1945. We had to wait until The Deathly Hallows for further information on the Wizard who would turn out to be a vitally important character.

14. He Was Expelled From School For Practicing The Dark Arts

Grindelwald’s love for the Dark Arts is proven beyond doubt by the fact that it got him expelled from the Durmstrang Institute, the Scandinavian wizarding school well-known for actively encouraging the use of them. Poison-pen journalist Rita Skeeter described Grindelwald as being “as precociously brilliant as Dumbledore” in her scathing biography of the latter, though she also claimed that he refused to channel his abilities into academic success and instead focused on a series of “twisted experiments” that even Durmstrang could not turn a blind eye to.

Of course, Rowling made it quite clear that Skeeter’s words are not to be trusted, though on this occasion her sources happened to be accurate, as Dumbledore himself made mention of the aforementioned experiments while discussing Grindelwald with Harry. It is revealed that the young Dark Wizard had a long standing fascination with magical artifacts and that chief among his goals was the procurement of the Deathly Hallows. Grindelwald went as far as adopting the symbol of the Hallows as his own personal emblem, carving it on the walls of Durmstrang before he left the Institution in disgrace.

13. He Turned Dumbledore Against Muggles

After his expulsion, Grindelwald traveled to Godric’s Hollow, England, where he was to spend the summer with his Great Aunt, the famed magical historian and writer of Hermione Granger favorite book, A History of Magic. This is where the teenage Grindelwald first met the Dumbledores, who had recently become residents of the Hollow. He and Albus Dumbledore struck up a bond over time as two wizards of a similar age and similar intellect, both highly skilled with a wand and both with great ambitions of putting their talent to use.

The pair’s relationship began as one based on convenience, with Dumbledore seeing Grindelwald as a window to the far-flung magical places he would never see while stuck in England caring for his young sister. Grindelwald, on the other hand, found mental stimulation in an intellectual equal who was keen to listen. As their friendship blossomed, they began a plot to overthrow the Statute of Secrecy and bring wizards out of hiding to establish rule over the Muggles. Using the motto "For the Greater Good", they planned to leave Godric’s Hollow and spread their message of dominance throughout the wizarding world.

12. Dumbledore Fell In Love With Him

As their relationship developed from one of mutual interest to one of t goals, the way Dumbledore felt about Grindelwald also evolved. Dumbledore fell in love with the dashing foreign wizard, described in the books not only as a brilliant mind but as a handsome young man, with golden blond locks and a “merry, wild” face. Rowling compared the way in which Dumbledore fell for Grindelwald to the way that  Bellatrix Lestrange felt about Voldemort when she first revealed the Hogwarts heaster’s sexual orientation during a book reading at New York’s Carnegie Hall in 2007:

“Dumbledore fell in love with Grindelwald, and that that added to his horror when Grindelwald showed himself to be what he was. To an extent, do we say it excused Dumbledore a little more because falling in love can blind us to an extent? But, he met someone as brilliant as he was, and rather like Bellatrix he was very drawn to this brilliant person, and horribly, terribly let down by him.”

Rowling added that she had to intervene during the writing process of The Half-Blood Prince film adaptation after she read a draft that had Dumbledore lamenting about a girl he used to know, leaving a simple note in the margin that read “Dumbledore’s gay!” Unfortunately for Dumbledore, Rowling has also insisted that his feelings for Grindelwald were never reciprocated.

11. Aberforth Stood Up To Him

When Albus Dumbledore’s younger brother Aberforth learned of his brother’s plans to leave Godric’s Hollow and set off on a worldwide quest by Grindelwald’s side, he was furious. Albus was the legal guardian of their younger sister Ariana after the death of their parents, who had both ed away in circumstances involving their troubled daughter. Their father died in Azkaban after being imprisoned for taking revenge on some Muggles who attacked Ariana for practicing magic, and their mother was killed when Ariana (who was never the same after the attack) accidentally set off a magical explosion.

Needless to say, Aberforth thought Albus should remain by his sister’s side where he was needed, though Grindelwald didn’t see it that way, as the younger Dumbledore brother explained to Harry, Ron and Hermione in The Deathly Hallows: "Grindelwald didn't like that at all. He got angry. He told me what a stupid little boy I was, trying to stand in the way of him and my brilliant brother. Didn't I understand my poor sister wouldn't have to be hidden once they'd changed the world, and led the wizards out of hiding, and taught the Muggles their place? And there was an argument... and I pulled my wand... and he pulled out his."

10. He Started The Duel That Killed Dumbledore’s Sister

With an ego to match his intellect, Grindelwald took exception to having a wand drawn on him and he didn’t hesitate to get the first spell off. The former Durmstrang student used the Cruciatus Curse on Aberforth, one of the three Unforgivable Curses. Dumbledore, despite his professional and personal iration of Grindelwald, couldn’t stand to see these curses used, least of all on his own flesh and blood. He stepped into the fight to defend his brother.

With Ariana out of sight, a three-way duel broke out and the curses began to fly. As the fight raged, the curious girl couldn't stand to remain hidden and entered the room, walking right into the fray and getting hit with a stray curse that killed her instantly. Although Aberforth blamed Albus for what happened that day (famously breaking his nose at their sister’s funeral) he revealed to the trio in The Deathly Hallows that he couldn’t be sure who had cast the spell that ended Ariana’s life: “The flashing lights and the bangs set her off, she couldn't stand it... and I think she wanted to help, but she didn't really know what she was doing, and I don't know which of us did it, it could have been any of us — and she was dead."

9. He Fled Britain In Search Of The Deathly Hallows

Fearing retribution from the death of his friend’s sister, Grindelwald fled Britain and began his search for the magical treasures he had desired since he was a schoolboy and was prepared to devote his life to. The Deathly Hallows had always been part of his agenda, even before he met Dumbledore at Godric’s Hollow. In fact, the budding Dark Wizard only visited his Great Aunt Bathilda in the little English wizarding village because he knew that Ignotus Peverell, the first owner of Death’s own Cloak of Invisibility, was buried there.

While Dumbledore was only interested in the procurement of the Resurrection Stone so that he could see his dead loved ones again, Grindelwald intended to find every Hallow and make himself invincible in the process. He knew that the wizard who possessed all three Deathly Hallows would be the Master of Death. With his presence in Godric’s Hollow no longer possible, he set his sights on the most sought after Hallow of them all, the notorious Elder Wand.

8. He Became The Most Feared Dark Wizard Of His Day

Grindelwald’s digging into the timeline of the Elder Wand lead him to a man by the name of Gregorovitch, a world-renowned wand maker who had been studying the famous wand's properties as part of his efforts to duplicate them ever since it came into his possession. He was never given the chance to finish his experiments, however, as the sprightly Grindelwald broke into the wandsmith’s shop through a window and stunned him, thereby winning the allegiance of the ancient elderberry wand.

With one of the three fabled Hallows in hand, Grindelwald cut a bloody trail across Europe that lasted decades, murdering those who stood in his way (the grandfather of Bulgarian Quidditch star Viktor Krum is revealed as one of his many victims in The Deathly Hallows) and erecting the prison fortress Nurmengard to hold his enemies. The extent of his exploits has become even clearer recently with the release of Fantastic Beasts and Where to Find Them, which reveals that Grindelwald’s campaign in Europe wasn't going unnoticed by Americans, who feared that the Dark Wizard’s attempt to overthrow the International Statute of Secrecy "could mean war".

7. Dumbledore Initially Refused To Face Him

As Rowling mentioned during her outing of Dumbledore, his love for Grindelwald made watching his rise to power through nefarious means all the more difficult, and perhaps excused his early hesitation when the wizarding community began a rally cry for him to face his former ally in battle. Dumbledore was Head of Transfiguration at Hogwarts at the time and getting a reputation as a potential future Heaster. He was someone with enough skill to stop Grindelwald’s reign of terror on the continent.

Later, as Heaster, Dumbledore told Harry the truth about why he delayed meeting Grindelwald until his shameful behavior finally forced his hand, and it all relates back to the duel at Godric’s Hollow: “While I busied myself with the training of young wizards, Grindelwald was raising an army. They say he feared me, and perhaps he did, but less, I think, than I feared him... It was the truth I feared. You see, I never knew which of us, in that last, horrific fight, had actually cast the curse that killed my sister... I think he knew it."

6. His Eventual Duel With Dumbledore Was Legendary

Grindelwald and Dumbledore hadn’t seen each other for 45 years when they finally came face-to-face for a duel that would determine the outcome of the Global Wizarding War, a conflict that had gripped the magical world for decades. Grindelwald had raised an army with the purpose of overthrowing the various Ministries of Magic across Europe and establishing a new wizard Empire based on the enslavement of Muggles the world over. Despite his fear of what Grindelwald might tell him, Dumbledore was left with no choice but to track him down.

The famous confrontation was later described by Dumbledore’s old friend and eyewitness Elphias Doge as the greatest wizarding duel of all time, lasting an incredible three hours and ending with the Dark Wizard’s defeat and arrest. What Doge didn’t realize at the time was that he had just witnessed the Elder Wand change allegiance from Grindelwald to Dumbledore, who would remain its owner until he was disarmed by an oblivious Draco Malfoy, shortly before his murder at the hands of Severus Snape.