General comments:

A big level (see map) and the hardest so far. As the name suggests you'll run into quite a few Phantasms. Have the Blue Crystal ready. Unlike the previous levels which are corridor based this level has large open spaces and it's easy to get ambushed.

No matter which ladder you come up (left or right) you're going to be attacked from all directions right at the start. Have fun! ;-)

Conversations with the Dead:

Read the Conversation with Claude (left of map).

So this is Claude. If you remember both Hans and the unamed German on They May Be Slow... respond to the name Claude even though the name is never mentioned until now. Oddly neither of them will respond to the name Gunther even though it arises early on along with the names Hans, Behrens and Joachim. So what do people have against Gunther?

Items to find:

Large Pearl (you get one point for this and it's also worth $11.0K)
One Walther P4 Pistol.
Nineteen Walther P4 Magazines (one loaded in the pistol).
One MP-41 Magazine beside a rock.
Nazi Propoganda.

Points to note:

When you grab the Pearl you total points will increase to 8. Since this is a further four point increase you get an additional 2 health units (total health = 10 units).

The Official Hints Book has this to say on the subject of the Pearl.

What does the Pearl do?
Other than increase your score, and thereby your vitality, it serves as the title to a really lousy story by Steinbeck.

"The Pearl" by American writer John Steinbeck tells the story of a poor Mexican indian pearl diver, Kino, who finds an extraordinary large pearl. Hoping that it will bring a better life for his family, he soon discovers "that the rare gem is instead a conveyor of greed, envy and ultimately death". Interestingly enough the story is based in Mexico in the 1930s. If you remember the manual had this to say about the Pyramid:

Only during the last few centuries has the god begun to effect changes on the surface of the Earth. Grotesque creatures have been sighted deep in the trackless forest of the Yucatan, and strange rumors of an ancient pyramid- which is neither Aztec nor Mayan- in the same area have been circulating in the archaeological community since the early 1930's.

The single MP-41 Magazine might make you wonder if there is a Schmeisser MP-41 machine gun lying around nearby.

The secret teleporter on this level doesn't take you back to the teleporter room on They May Be Slow... it drops you instead in the top right hand ladder room on Lock&Load. Was this intentional? The other set of secret teleporters work teleporter room to teleporter room.

Monsters to kill:

Headless, Zombies and Phantasms.

Decisions to make:

You see a ladder going up. Ascending to Ascension.