Through The Gate
The Darkness: The Forsaken Prince #5. Second Mission, it can be found on The Tangled Shore in the High Plains, a little bit from where you spawn.
Pressure
The Light: Ghost Stories #1. Second Mission, It can be found on The Tangled Shore in the High Plains, a little bit from where you spawn.
To Map The Unknown
The Light: Ghost Stories #23. Second Mission, it can be found in the same room as the Spider NPC on the Tangled Shore.
This was very helpful. Thank you!