I kind of came in with a similar idea. Except, it would be the final boss. Basically how I see it is the boss would start off as an exact mirror to you. Same armor, same level and skills, same weapons, same rings, etc. He wouldn't be too terribly aggressive during this initial stage. However, the kicker would come at around 3/4 to half health. Up until this point, the game will have been tracking your playstyle and analyzing its weaknesses. The boss will then gain to ability to change his armor, weapons, and rings, and reallocate the points to other skills on the fly so as to best exploit those weaknesses. He will have access to every item in the game, meaning he can truly exploit your weaknesses as greatly as possible. As the fight continues to progress, he will gain the ability to have a "higher level" than you, meaning his skills will only increase. His weapons and armor will become imbued and leveled up more so than your weapons are. He will become, for all intents and purposes, your greatest enemy, and your ultimate challenge. You must learn to adapt and change your strategies just as quickly as he does, or you will fail. Killing him will earn you 50K souls, The Soul of the Domineer, and the ability to ascend a weapon of your choosing past +10 to a rare, special weapon at your friendly neighborhood blacksmith. Trading the soul can earn you a Hex that temporarily copies every characteristic of an enemy you're facing in PvP, but also increases every skill of theirs by +10. That, or a sword that inflicts damage of the effect that the enemy you're facing has the least defense to. You can also pop the soul for another 50K souls.