Few gaming accomplishments feel quite as good as completing an archaic series of events deep into an adventure, only to find yourself face-to-face with an enemy that most players didn't even know existed. From celestial beings and playground legends, to inside jokes and series throwbacks, here are our 10 favorite secret bosses in video games.

10. Culex (Super Mario RPG)

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Back in '95, the idea of Square and Nintendo making a game together seemed impossible, and yet lo and behold Super Mario RPG was gifted to the world along with its ridiculously tough boss Culex. In the dark corners of the game’s Monstro Town resides a Culex, a foe who shrugs off Super Mario RPG's two point five D aesthetics, and goes straight up Final Fantasy on the plumber and his crew. Seeing his iconic crystals, hearing the Final Fantasy music, and finally taking down Culex was one of the most satisfying moment of the entire game.

9. Driviks, The Chosen (Destiny)

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Destiny fans are about as hardcore as they come, so it’s no surprise that Bungie’s ambitious online shooter made its way onto this list. This secret boss was discovered by the community and is only available when the Daily Heroic mission ‘LOST TO LIGHT” shows up randomly. In classic Bungie fashion, as the level collapses to its end, there is a hidden path that leads Driviks, the Chosen. Players have a mere 10 minutes to complete the task and -- of course -- Driviks is not easy to beat. Your reward? The highly sought after and must-own Black Spindle exotic sniper -- and this is the only way you’re going to get it.

8. Karstaag (Skyrim)

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The worlds of the Elder Scrolls games are rife with secrets, but few are as cool as Karstaag in Skyrim. Going through the rigorous steps to summon the ghostly Frost Giant is quite the feat, but the reward is absolutely worth it. If you manage to slay the beast, the Dragonborn is given the ability to summon the powerful creature three times. Trust us, it’s worth it.

7. Yama (Spelunky)

Spelunky is a game rife with secrets, and it has a catalogue of YouTube videos and mind-melting speed runs to prove it. But deep down the well of Derek Yu's rogue-platformer is Yama, the game’s ultimate boss. If you manage to fulfill the litany of requirements needed to enter the hidden area of Hell, you’re rewarded with an incredibly-tough fight against King Yama, the toughest foe in a game packed with things that want you dead.

6. Moon Presence (Bloodborne)

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From Software is no stranger to brutal, macabre, and straight-up disgusting bosses. But none are quite as memorable as Bloodborne's

5. Sephiroth (Kingdom Hearts)

Yeah yeah, this is one of the most memorable villains in all of video games. But his presence in Kingdom Hearts was an amazing surprise, and provided a wonderful. cherry on top of the sundae that Square and Disney concocted. After you've made your way through the colorful worlds of our childhood, you're able to face Sephiroth, Final Fantasy VII's iconic villain. Sora's battle with the one-winged angel is every bit as epic and tough as Cloud’s fight in the PS1 classic.

4. Red (Pokemon Gold/Silver)

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The ultimate battle in Pokemon Gold and Silver is also one of the most emotional fights on this list. Long after you've conquered Kanto and Johto's 16 gyms, you can earn the right to prove that you're the best...like no one ever was. And to do that, you have to accept one final showdown with Red, the hero you played as back in the original Pokemon Red or Blue. His crew of Pikachu and full-evolved Gen-1 starters makes this battle an unforgettable and nostalgic masterpiece.

3. Reptile (Mortal Kombat)

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Back in the era of playground myths and legends, few were as memorable as the fabled "third ninja" in Mortal Kombat. Aside from Scorpion and Sub-Zero, this green triplet was said to reside at the heart of the game's brutally-iconic Spike Stage. Sure enough, if you manage to fulfill the strange list of requirements, you’re able to face off against the acid-spewing ninja, who later became a series-staple.

2. Cow King (Diablo II)

I'm going to be honest - it's gonna get a little weird here. Deep inside the dark, gothic world of Blizzard's Diablo II lies a terror pulled straight from the bowels of hell. Yes, we're talking about...the Cow King. Despite Blizzard’s insistence that there is no “Cow Level”...there totally is. If you manage to get there and slay your way through the horde of bovine beasts, you’ll come face to face with the strangest enemy in the entirety of Sanctuary.

1. Emerald and Ruby Weapon (Final Fantasy VII)

It's fitting that this list culminates with with a pair of foes from one of the most memorable RPGs of all-time. After Sephiroth summons Meteor, this pair of uber-powerful enemies emerge from their slumber and exist to for the sole purpose of making Cloud and company’s lives a living hell. Emerald’s underwater home necessitates finding a specific Materia, but even then, good luck at chipping away at its one million HP. Likewise, Ruby Weapon has insane defense, impossibly-strong attacks, and the ability to completely remove party members from the battle. Anyone who can say that they conquered both Weapons has some serious video game street cred.

Did a favorite secret boss of yours not make the list? Let us know!