There was a colossal difference between a Level 19 player and a Level 20 player. Crossing that threshold unlocked the third tier of talents—skills so powerful they could redefine a playstyle.
Ryan knew this firsthand. His enchanted weapon, Command, came from his Retribution build and had completely changed the way he played. The skill's sheer power made him almost untouchable at his current stage. Its damage and utility were so overwhelming that he had abandoned every other enchanted weapon he'd ever obtained. Even those he picked up later couldn't compare to the might of Command.
It was the same for other classes. A Protection Paladin who reached Level 20 gained a new talent that drastically boosted their survivability. That single step into the next tier of play made them feel like an entirely different character.
And what applied to players applied to monsters as well.