The Stone Table is a conduit of power through the blood spilled on it to which ever Court has domain over it: Summer or Winter.
It passes between the control of the Summer and Winter Courts of Faerie, switching hands at the summer and winter solstices. It is the place the Queens call forth when the Sidhe wish to spill blood.
The Stone Table is a massive slab of stone resting on four stumpy pillars, located on a fifty-foot mound located at the center of a bowl-shaped valley named after it; other stones are circling it. The structure is faintly illuminated in subdued blues, purples and deep greens—Winter colors being after the equinox. Runes writhe on the table's surface that seemed to be from different sources: Norse, Egyptian and others. The runes liked neon under the flashes of lightning.
The air around the table shook and, as Harry Dresden's hand passed through it, skin rippled as if by wind. The power in the table itself could be felt through touch and "buzzed through the flowing runes like electricity".
As one Court gains control over it, the ground surrounding the Table will take on the color and character of that Court—warm greens for Summer and cool blues for Winter.
In the series
In Summer Knight, the Leanansidhe showed Harry Dresden the table warning him to never let Mab bring him there. She asked him to use his Sight so that he could understand what was at stake. The Summer Lady Aurora tried to use the Stone Table to gain power.
Harry used his Sight to See the Stone Table and the landscape surrounding it. It seethed with conflicting energy. On one side it was filled with flowers, greens and golds and flashed of color and points of brilliant light. The other side were crystal ices of cold blue, purple and greens advancing in some places and melting in others, heat against cold. The powers played against each other like a giant chess game forming a pattern of squares of gold and red against "dead blocks" of darkness. The Stone Table at the center was the only solid area of Summer's power in green and gold while Winter pressed closer.