Yao Guai Den Note

The yao guai den note is a holotape in Fallout 3.

Location
It can be found on the body of a dead settler in the yao guai tunnels. The note states they were building a settlement in the den and had blocked it off from the rest of the tunnels. However, the location of several raiders' bodies suggest the barrier was breached which may have accidentally let the yao guai in.