Vault of the Blue Golem (Patreon)

Up in the hills is a small crater-like depression with a mostly smooth floor and a pair of heavy metal doors that lead to some place in the hillsides.

The doors open twice every 6-9 months. Once to allow the Blue Golem into the crater to begin its wandering, and once again exactly 10 days later when the Blue Golem returns.

The Blue Golem walks the lands nearby seemingly at random for those ten days – usually just walking from one place to another and then moving on to the next. On rare occasion the golem stops to collect something small and place it in a box build into its shoulder. Usually this is a plant or a small animal, but of course tales include it kidnapping children or seeming to want specific body parts from those that come too near.

https://dysonlogos.blog/2019/02/07/vault-of-the-blue-golem/