From The Heretic Knowledge Vault
As far as we can tell, the Sleeping Sexton is a distinctive rock formation in the mountains north of the small Veracian town of Heamish. It attains some significance as a result of the presence in Heamish of the Hamael family, nearest known relatives of the mysteriously fugitive Father Egbert. Head of household Wilbur Hamael works in a mine on the slopes of the Sleeping Sexton (at least until he's inexplicably teleported to the Mountains of Madness), while his wife Mildred, Egbert's sister, stays home and cares for their children, the unexpectedly lethal Jason and an infant. These worthies are visited by Argus and Brother Miguel as they try to figure out what became of Egbert.
The Sleeping Sexton also figures in a bit of misdirection by Miguel that's intended to throw off pursuit by someone masquerading as Gordon Grumiel, the last person known to have seen Father Egbert alive. ("Alive" here refers to Egbert, not Mr. Grumiel, who has met an unfortunate end in Saus.) It's now known that this impostor was one "Arkie" Arganial, who in his turn met a messy demise in the unpleasantness around Centoriel. However, this had nothing to do with the Sleeping Sexton.
For a sense of what this formation might look like, check out this image of its namesake in the real world, in the mountains of Colorado (it's the ridge in the background). The Veracian version isn't as high, and therefore wouldn't have snow on it under normal conditions, but you get the idea. Note that the fall foliage wouldn't be present at story time either, most of the events of Errant Road happening in the spring, not fall.