The Final Charcoal Stair Sketch is the sole surviving drawing from a series of charcoal studies created during a severe overnight storm within the observatory tower. Originally intended as architectural practice sketches of the observatory interior the drawings progressively incorporated recurring imagery associated with Archive memory events including descending staircases impossible geometric arches and lantern-lit subterranean spaces. All preliminary sketches were destroyed before dawn with the exception of a final sheet preserved within the western desk archive. The drawing depicts a descending stairway illuminated by hanging lanterns beneath distorted arches consistent with geometry documented in related artworks and the Geometric Archive Tablet. A solitary figure appears partway along the staircase looking upward toward the viewer. The sketch was created during a documented bell event accompanied by a brief recovered memory episode. The work is considered part of the Archive's growing Memory Artworks Collection and may represent involuntary visual documentation of remembered locations rather than imaginative construction.