Egypt is home to dozens of species of deadly mushrooms. The Test of Darkest Night is taken in 7 stages, and involves building your body's resistance to toxins found in freshly grown mushroom species.
Note this triggers at any 7 in your regimen (eg. 2 of one type and 5 of another will complete principle).
Somewhat confirmed. I passed the principle above after the bug-fix where I had 7 of one mushroom but hadn't passed, but ate another mushroom of another qualifying type and immediately passed. - Aperio
You are given 4 randomly selected mushroom types to find and ingest fresh from the earth (you cannot use mushrooms already picked). Once you have eaten 7 each of at least 2 types you can return to any UBody for a new list and a permanent point of Constitution.
Somewhat confirmed. I ate 7 mushrooms of one type in the second round and did not advance. Will try to eat a split of types like the principle next to verify that it must be 7/7 for each type. - Aperio
Somewhat confirmed. I ate all of the four mushrooms in my first list. When I turned it in I got 2 Con pts. So perhaps we get a con pt for every two completed shrooms we turn in? -inshepsut
You pass the test upon reaching 7 permanent Constitution.
If you find mushrooms around low buildings like fountains, remember that "Utility->Make nearby portables look like bags" can come in handy
Note: It's safe to have "Auto-take piles of up to 50 portable items" enabled with this test, you don't have to disable it to get the menu
Mushroom Info: Mushrooms
Mushroom Tracking: Shroomdar