Which episode of Yu-Gi-Oh do you see the Dark Sage?

The Dark Sage doesn't appear in the original Yu-Gi-Oh! anime series.

The Dark Sage is a monster card that was introduced in the Yu-Gi-Oh! GX anime series. It's associated with the character Jesse Anderson, a duelist with a connection to the "Sage" archetype.

You'll see the Dark Sage card in action in various episodes of Yu-Gi-Oh! GX, primarily in the episodes where Jesse Anderson is featured.