Layout:
-Basement wiring controlled by one circuit breaker, including:
-2 light switches controlling the sconce light fixture in the stairs to the basement, one top, one bottom.
-Bottom switch also has a 2nd switch to inside the basement to 2 basic single bulb light fixtures.
-There are 2 electrical outlets in basement.

Project:
-Replace one of the overhead light fixtures with a single gang outlet.

Existing wiring at light fixture:
-3 runs of nomex to the box.
-3 black wires, 3 white wires, 2 red wires, 3 ground wires in the box.
-To the light fixture itself, 1 red pigtail and 1 white pigtail.

Action:
-I replaced the light fixture with a basic single gang outlet, and wired ground wires to ground terminal, white pigtail to one silver terminal, red pigtail to one brass terminal.

Result:
-Stairway sconce light inoperable from either top or bottom switch.
-Outlets in basement are dead.
-New outlet and other exiting basement light are live with the switch on.

Question:
Why did I lose my stairway light/switches?
Why did I lose my 2 basement electrical outlets?

What did I do wrong? Any tips are appreciated!