Queen – “The Trap” [Campaign 1, Mission 4]

Capture the castle - go to the bridge - trigger the script - a little further down is the prophet - next to him is the entrance to the dungeon - inside, at the top, is a grave that needs to be searched - you'll get boots; it's best to approach with an empty boot slot, otherwise they might glitch and end up in your inventory in an invisible state (try right-clicking the slots in that case).
The map is classic, meaning you progress from bottom to top.