Main Sewer Junction - Batman: Arkham Asylum
As you enter this area you get the Riddle: 'A puzzle has many sides, but only some are visible.'
As you move forward you notice that there is Titan in the sewers and call Oracle to check on that, and if you look around you will see that this area also has thugs. Ahead and to the right is a pod to kill, then you can climb the wall here and jump to the catwalk, then the next catwalk and kill another pod. Now run up the first fallen pillar, and look left while you get more info from Oracle.
Jump across and reach the second fallen pillar, and head up, and at the top look to the left for a narrow ledge you can climb and then shimmy around in order to pull yourself up to the next level. Climb again and notice the Riddler Trophy here – pick that up and you get 200 XP and unlock Commissioner Gordon's Character Trophy! Now look up – see the Riddle Mark? As before, line this up so that it makes the complete mark and then scan it to complete the Riddle for this area.
Now drop down, crouch and climb down and shimmy and drop back down, and then head over to the next pod and kill it. Turn around and look at the gap here across which there is a Riddler Trophy and a pod – we are not going here yet :)
This is a little tricky and requires good timing, but there is a alcove ledge below the ledge across from you, directly beneath that Trophy – you want to glide down onto that ledge then turn around and Line Launch to the alcove ledge directly across from that and snag the Riddler Trophy here, get your 200 XP and unlock the Scarecrow's Character Trophy. Now Line Launch back and jump the gap to the waterfall and run up the fallen pillar.
Retrace your steps until we get to the ledge where the shimmy point was where we went up to solve the riddle, then Line Launch over the gap to the right of the pod, drop down and kill it, then go collect the Riddler Trophy nearby – which will also unlock another challenge.
Now run past the dead pod and climb the wall at the end, climb again and then follow the route up to the highest point to trigger the new objectives – now you know what you really need to do about the Titan in the water! Now look north in the direction of the bad guys – there is a ledge you can Line Launch to there – so do that now.
Climb three times and run out on the ledge and up the ledge-ramp thing here. See that Trophy below and to your right? Drop down and grab that, then glide back to the broken aqueduct and climb back up to where we just were before we dropped down to get this Trophy.
Target the weakened wall with your Grapple and rip it down, then target the three Thugs here with your Grapple and rip THEM down! Mahahahahaha! Take out the last Thug here and then look in Detective Mode at the inspection panels. The water purity on this side of the valves is find, but you will find down a short corridor some infected water in the pipes – and if you look to the right here you will find the fourth Patient Interview tape for Killer Croc – grab that and give it a listen.