I'll assume you follow Gregor's advice without getting cold feet.
You grab the fifth orb and move on to the central room with the circle, where you place the five orbs in the five floor slots.
The whole room starts shaking. The floor inside the circle drops down a foot or so, then splits into five sections along the curved lines. The floor sections start retracting, revealing a deep dark pit beneath them. You jump back to avoid falling down.
Eventually the floor in the circle has retracted completely, and the room stops shaking. The pit stretches down into darkness; you can't see the bottom of it. But soon you notice something coming up from the blackness. It is a sword, floating in the air and steadily rising upwards. When it comes above the lip of the pit it changes direction, going out over the solid floor where you are standing. There it drops down with a clank.
The sword is similar in style and size to the sword wielded by the ice person, and now wielded by Gerald, but this one is much more intricately made. This is what it looks like.