What is the title object in Lovecraft's "The Silver Key"?

The title object in Lovecraft’s “The Silver Key” is a silver key.

In the 1929 story, Randolph Carter has lost his ability to enter the imaginative dream world he once cherished. During a dream, his deceased grandfather tells him about a silver key hidden in the attic of his ancestral home. Carter finds it, carrying mysterious arabesque markings, and takes it back to the rural Massachusetts setting of his childhood.

The key is more than an ordinary household object. It becomes a magical link to Carter’s past and enables him to enter a cave associated with his childhood, effectively returning him to his younger self and escaping the limitations of ordinary adult life.

The story was written in 1926 and first published in Weird Tales in January 1929. It continues Carter’s dream-centered adventures and precedes the co-written sequel Through the Gates of the Silver Key.