The map is procedurally generated. Map layout, Number of Secrets and Secrets Locations will vary for each playthrough. In Creeper woods, number of secrets will vary from 2 to 10. One Secret will always be taken by default as the mission is launches. Two of the secrets have fixed location. Location for rest of the secrets varies. One Secret Rune can be collected only after you have completed the entire main campaign. So, in your first playthrough you wont be able to collect all the secrets. Check the video at the end of the page if the written walkthrough is not clear.
You’ll get it by default as the mission is launched.
This secret has a fixed location. Check the picture below.
This secret is an entrance to a crypt and has a fixed location. Check the picture below.
Next few secrets will have varying location on map. These secrets will always be found in portions extending into the walls. A Couple of examples are shown below.
Secret 8 (Can be collected only after completion of Main Campaign)
This secret is in the area where you get the objective to free 5 villagers. In this area there is a movable rock and just next to it you’ll find a pressure plate that will move the rocks. Press the plate as shown in picture 2 below and it will open a secret passage. Go inside and collect a Secret Rune. Collecting 9 Runes will unlock a Secret Cow Mission.