Missing/inaccessible Secrets on E4M3, Sever The Wicked:

Note: A Secret score below 100% is normal for this level,
due to a minor problem with this level's construction.  (A
score of 90% is the normal maximum.)

When you first appear on this level, you'll be standing on
a long platform located in the middle of the north half of
the map, and you'll be facing west.

Head west, off the end of the platform, and proceed forward
to the stairs leading underground.  Go down the stairs and
turn left/south.

Head up the next stairway ahead of you, and turn left/east.
Walk a few paces forward, and search the left-hand wall for
a secret panel.  (This panel also opens when you approach
the wooden door nearby to the south.)
Open that wall panel and step through to receive credit for
a Secret discovered.

Step back through the panel and go back down the stairs you
just walked up.  At the bottom, continue forward/north a
few paces, then turn left and head west, and go through the
window-like opening you'll see there.

Ahead you'll see some torches.  Step between the 2 nearest
torches, and the floor ahead will drop down momentarily,
revealing a teleporter booth ahead and to the right/north.
Step into the teleporter before the floor rises again.  (If
you don't get into the booth in time, simply step between
the torches again, or Activate the raised section of floor
from its southern edge, and it will drop down again.)

You'll be teleported to a pad at the southern tip of the
map, and you'll be facing north.  Turn left and head west,
and follow the path north and west again to step into a
small octagonal alcove where you'll see 4 torches.

Activate the north wall of this alcove to open a hidden
wall panel and reveal a stairway beyond.  Most of this
level's 22 secret areas are arrayed along the steps of this
stairway.  Simply walk carefully across all the steps, and
into the room at the top of the stairway (where you can
find a Soul Sphere/Supercharge item), to receive credit for
finding the remaining accessible Secrets on this map.

Back down in the octagonal alcove, 2 small triangles of
floorspace are flagged as Secret, and are also occupied by
torches.  Those torches prevent the player from stepping
into the spaces they occupy, and this prevents the player
from getting credit for those Secrets.

PC Doom players can click here to access a demo that shows
how to find all accessible "official" Secrets.