There are 8 different Darkling outfits, 2 of which are optional
and are obtained by dialling a number on a phone. You only need the
6 listed to obtain the achievement.
1. Chapter 1
When you first go to visit Jenny, exit the subway and
walk straight. There will be an alley to your left. At the entrance
the alley is a box with an outfit in it. Press A to smash
the glass and take the outfit.
2. Chapter 1
After running away from the Helicopter in China Town,
you will travel through a pool hall. One out of the Hall and into
an alley, there will be a bum. In this same alley, look for a
door with a vent above it. Shoot out the vent
and send your Creeping Dark into it. You must break the 2 lights in
the room and you must be very quick. You may run out of power,
but just let it recharge and try again.
3. Chapter 3
Jimmy the Grape will send you to kill Petey “Pajamas”.
He is in Grinder’s Lane, which is very small so it won’t be hard
to find him. As you exit the subway, turn left, then turn left
again when you get the chance. 2 men will be
guarding the door and 2 men will be inside. Kill them then kill Petey.
The outfit will be in the main room.
4. Chapter 3
Vinny Mortarello will have 5 hits for you. After
taking out the first 4 hits, you will be sent to Gun Hill for the
final one. Near Eddie Shrote’s apartment, still outside in the
alley, will be an open window. Send your
Creeping Dark in there and kill the man, in the room will be an outfit.
5. Chapter 3
Dana Cutrone will be sitting in Canal
Street Station on a bench.She asks you to go to her apartment
in Chinatown to get the keys. Right when you exit the subway,
walk straight and turn right at the intersection. Now turn
left down an alley and look for the door to the apartment.
Tell her boyfriend to get out and enter the apartment to
find the outfit.
6. Chapter 3
While on your way to the Turkish Baths, you will
have to travel through City Hall Station. Along the tracks, right
before you meet the two homeless people, will be an abandoned
train cart. At the very back is the last outfit.
Credit goes to Lvl99blkmage. In Achievement Guide section in Gamefaqs.com