Wait wut just happened. (No spoilers plox)

So my now corrupted save file in Demon's was putting down his blue eye stone to help out someone so I could become humans agains.

Almost instantly I was being summoned, I started happily doing a strange dance but then there was a cut scene, some old man who was sitting in his chair made out of chairs gave me his clothes and put them on my head, and then I had to kill a die hard demon's fan with my terrible armour but luckily I had my skill from my die hard dark souls fandom.

Wut happened.

Only explain what happened to me, not what will happen to me or anything like that.

No spoilers.

You became the end boss. The way the boss at level 3 is that once you put down your sign there is a good chance you will be summoned as the boss to fight the player.

You were summoned by the boss of an area to fight against the person trying to beat the level.

EDIT: Ninja'd lol.

I actually likes Xachs answer better, less spoilers, I didnt want to know id be fighting another player at the end of the level.

You got a taste of why Demons souls rocks so hard

The first time that happened to me I was new to the game and I was so confused that I died instantly the other guy probably thought it was the easiest boss in the world I don't think I even hit him lol

The Archdemon of Tower of Latria (World 3) has the ability to forcefully summon any player who tries to engage in online play. It applies to both summons and invasions. As such, you will becomes somebody's Archdemon. You retain everything you had, but you get additional HP (I think you get 2000) and as your HP gets lower and lower, the headpiece you have will start summoning yellow magic orbs, that will automatically fire at your enemy. You can actually learn this spell if you manage to defeat this particular boss in your game, but the spell works slightly different when player uses it.

If you manage to win as the boss, you will get rewarded by the golden tornado headpiece, which will increase your Magic damage by 20%, but also lower your Magic Defence. Made by SWAG u industries.

It happens randomly, you can't force the game to choose you, nor evade it. If it happens, go along with it. Don't quit, or anything. If you don't wanna PvP, just let the host kill you and make his day.

Lastly. This can happen thorough the whole of World 3, but the closer you are to the Archdemon the higher the chances are it will happen.

EDIT:
I'm not sure if this contains any spoilers. I said nothing about the story, or the reason why, or exactly where this happens.

That was my reaction the first time it happened to. A real WTF moment. I fought the guy though, instinct said Not to let a person kill me. I would later repeat the process several times and have amassed a few tornado head wraps. They are horrendous. I started leaving them to players that seemed new to me when Iwould co-op. I think iI may get back to this game. It has such a better atmosphere to it. Might even buy a different regional version and get a 2ndand trophy set lol