How does Dickens create mood in the scene when Pip returns to Satis House in Great Expectations?
There are actually a few occasions where Pip returns to Satis House after his discovery of the great expectations that he has. I assume you are refering to the final chapter of the book, where Pip returns after the end of his relationship with Magwitch and the subsequent loss of his expectations.
It is important that we realise mood is often created by setting, and so it is always vital with such questions to pay attention to setting. Note how Dickens creates a peaceful mood in this scene, in spite of a mist that lingers on:
A cold silvery mist had veiled the afternoon, and the moon was not yet up to scatter it. But, the stars were shining beyond the mist, and the moon was coming, and the evening was not dark. I could trace out where every part of the old house had been, and where the brewery had been, and where the gates, and where the casks.
The evening is "not dark," which makes sure that the mood Dickens creates here is not an oppressive or scary one. Pip has returned for reasons of nostalgia, and it is clear from the way that he is able to see Satis House as it once was in spite of the massive changes that he remembers it so well as being part of a crucial stage of his life. Perhaps the most important piece of description we are given, that incidentally effectively foreshadows a happy ending for Estella and Pip, concerns the detail of the ivy:
The cleared space had been enclosed with a rough fence, and looking over it, I saw that some of the old ivy had struck root anew, and was growing green on low quiet mounds of ruin.
Of course, this detail is incredibly symbolic, as it refers to the desolation caused by Miss Havisham in both Pip's and Estella's life, but it also refers to the possibility of new growth, thus giving this final scene a mood that is optimistic and hopeful.