The Mummy Demastered (EP)

For this achievement, you need to visit every portion of the map (so the whole thing is lit up) and finish the game (because the achievement won't pop until the end-game statistics screen).

Some rooms are hidden behind destructible barriers, which means you'll either need grenades, C4, or the Ankh of Seker to access them. Compare your map to the completed map below, and look for passages to find your way in. Most of the rooms are pretty self-explanatory, so you'll probably get most of them like that.



One room, however, is kind of tricky to reach. It's in the lower left region of the map, just off the 3x3 square directly below one of the elevators. In fact, you may notice that you can't quite reach the very center of that square.

The solution is to use a dash boost. Make sure you have both the Scroll of Qebui and the Ankh of Seker enabled, and run down the long corridor to the right. Build up enough speed and you can jump and boost through the doorway, which will cause you to blow through the middle of the square room and straight into the little room on the side (which contains a health pack, too!).

Here's a brief video showing the process (I had already unlocked that area, so I'd already broken through the walls when I made the video):



Another note: Part of the map isn't accessible until after you defeat the final boss. You should have the map 95% complete if you go to the save room just before the boss. That's a good indication you're on track.

Yet another note: The Ankh of Seker is the only item necessary for this achievement that isn't story-related (I think). The Ankh is available after defeating the Scarab boss, and it's found underwater just to the left of the base of the clocktower (in the orange part of the map). It's in that single-square room 6 spaces to the left of the save room below the clocktower.