Nessie or the Loch Ness Monster has its appearance in Tomb Raider The Lost Artefact (Director's Cut).
Apparently, there are two versions of Nessie at this level. One is the robotic version, and another is the true version of Nessie. One time that we entered inside the robotic version you can see some planes of robotic Nessie, we can see that she has the shape of a plesiosaur, whereas the real Nessie is a marine serpent.
In the first level Highland Fling you can meet Nessi on three occasions.
1. When you step onto the huge stone bridge, look down to the right. In the mist you can spot the monster.
2. When you reach the pit with the green fluid you can look through the fence to spot Nessi again.
3. When collecting the 3rd Secret you will come very close to the monster. You will encounter a fire spitting creature that is in fact artificial. Inside you will meet some guards who are controlling Nessi.