Blizzard has been making great games for decades, but every developer has one game or franchise that truly defines them, and in their case, that game is World of Warcraft. It may have been released in 2004, but WoW is still the most popular MMORPG in the world, and it has achieved this by offering great gameplay and characters. It also happens to have some of the richest and most complex lore ever seen in a video game franchise.

RELATED: World Of Warcraft: 10 Trivia Fans Didn't Know About Warlocks

At its core, WoW revolves around the struggle between the Horde and Alliance, but they have been known to occasionally join forces, and this usually happens when their world is threatened by the Burning Legion. The Legion is comprised mainly of demons, and quite a few powerful beings are or have been associated with it.

10 Magtheridon

Magtheridon is a Pit Lord, which means he is a powerful demon who excels at melee combat and weakening his enemies; furthermore, he loves to instill terror. The Horde has a history of corruption, and it all stems from Magtheridon, who found his way to Draenor (now Outland) and corrupted the orcs with fel magic.

Magtheridon ruled Outland for 20 years until Illidan Stormrage and his Demon Hunters fled to Outland and overthrew him. Magtheridon is now Illidan's prisoner, as he is currently being held in Hellfire Citadel, where his blood is being used to create new fel orcs for Illidan's forces.

9 Kazzak the Supreme

The Doomguard is a demon race that functions as the Burning Legion's commanders and generals, and Kazzak is the Lord of the entire group. This elite demon was Kil'jaeden's Right Hand, and he was one of Archimonde's most trusted commanders when the Legion attacked Azeroth during the Third War.

RELATED: World Of Warcraft: 10 Things Fans Didn't Know About Mages

Most demon leaders choose to stay behind the lines, but Kazzak loves to throw himself into the heart of battle. He is responsible for reopening the Dark Portal, and he currently commands the Legion's forces in Outland.

8 Tichondrius

Those who played the RTS games have a greater understanding of WoW's lore, which means they know all about Tichondrius. He is the former leader of the Dread Lords, whose primary role is to serve as the Legion's strategists and tacticians.

Tichondrius was the mastermind of several Legion operations, including the destruction of the Quel'Thalas region and the siege of Dalaran. He also orchestrated the death of Uther the Lightbringer, which is why he was later given command of the Scourge. That command didn't last long though, because Illidan slew him with the power of the Skull of Gul'dan.

7 Mannoroth

Mannoroth is the former leader of the Pit Lords, and he was known for being a barbaric leader, but he was also a brutal and bloodthirsty fighter. At one point, Mannoroth was Archimonde's second-in-command, and he led the Legion to victories on several worlds.

Mannoroth fought in the War of the Ancients and led the first invasion of Azeroth. Thrall is one of the strongest champions the Horde has ever produced, and even he was no match for Mannoroth, who basically shrugged off one of the Warchief's strongest attacks.

6 Queen Azshara

Azshara is still one of the strongest mortals on Azeroth, and before she became the queen of the Naga, she fought in the War of the Ancients alongside the Burning Legion. While using the Well of Eternity, Azshara drew Sargeras' interest, and the Titan was able to entrance her with his power.

RELATED: World Of Warcraft: 10 Facts About Death Knights Fans Should Know

Azshara opened the portal which allowed the Legion to launch their first invasion of Azeroth. Mannoroth nearly attacked Azshara when she blamed him for the portal's destruction, and he quickly realized that only the strongest members of the Legion could defeat her.

5 Archimonde

Archimonde was one of the leaders of the Eredar, a race of talented magic-wielders who lived on the planet Argus. When Sargeras took interest in Argus, he offered the Eredar untold power if they joined the Legion, and Archimonde agreed.

Archimonde was ruthless and cunning, which is why Sargeras made him the Legion's field commander. He successfully led the invasions of several worlds, and he was responsible for Dalaran's destruction in the Third War. During the War of the Ancients, he killed a God named Malorne, which proves how powerful he truly is.

4 Kil'Jaeden

Like Archimonde, Kil'Jaeden was an Eredar leader who sided with the fallen Titan. He went on to become one of Sargeras' chief lieutenants, and he served as the Legion's top strategists, but he was also in charge of bringing new races into the Legion's fold.

Kil'Jaeden took Gul'dan under his wing, and he nearly destroyed the continent of Northrend with the Eye of Sargeras. He is also the one responsible for the creation of the Lich King. Kil'Jaeden invaded Azeroth through the Sunwell, and he fell after retreating from the Tomb of Sargeras.

3 Argus

Argus may be a fel-infused planet, but it also houses the soul of a Titan with the same name. His true name was Argus the Unmaker, and he was the final raid boss of the Legion expansion, where he became only the second enemy in the lore to ever kill the player's champion.

Titans are beings of unimaginable power, and although Argus was technically a newborn when players encountered him in the raid, he was still strong enough to cleave a planet like Azeroth in half.

2 Aggramar

Like Argus, Aggramar is a Titan, so he is automatically one of the strongest beings in the lore. Sargeras was originally tasked with eliminating the demon scourge, and Aggramar served as his lieutenant, but he was eventually betrayed and killed by his superior.

RELATED: World Of Warcraft: 10 Healer Tips To Avoid TPK In Raids

When a Titan dies, their soul still wanders the universe. Consequently, Sargeras was able to corrupt Aggramar's soul, making him a reluctant member of the Burning Legion. He also wielded a fragment of Gorshalach, a sword that belonged to Sargeras and is regarded as one of the strongest weapons in the WoW universe.

1 Sargeras

Sargeras is the creator and leader of the Burning Legion, but he was once the champion of the Titan Pantheon. He led the Legion against the Pantheon and ended up eradicating them single-handedly with his fel magic. He then went on to destroy thousands of planets.

It is because of Sargeras that the entire WoW story even exists, as he has been influencing events on Azeroth for thousands of years. Sargeras is responsible for burning Illidan's eyes and corrupting Medivh, while he almost destroyed Azeroth when he impaled the planet with his sword.

NEXT: The Elder Scrolls: 10 Things You Didn’t Know About The Daedric Princes