If you still need help with the missions from the Deadly Shadows campaign, please let me know.
I assume you are asking about A Mountain to Climb, mission 5 of the campaign. At the beginning of this mission, the player needs to find another way into the mountain castle, because the other side of the drawbridge is up.
On the right of the gargoyle statue on the east side, there is a hole in the railing of the accessible side of the drawbridge. Let yourself fall down onto the rock platform below and continue to the mountain castle from there. A glowing crystal lights the way.
Can't find the missions "The Enterprise", "Schulmod", "Mansion 48", the Japanese mission "The Drop", "Elevator Mission v1" (T1), "Elevator Mission v2" (T1) and the standalone releases of "Tuttocomb's Tomb" and "Escape from Guilesatpeak" in the database. Would be cool if these were added.