Batman – Arkham City: Hot And Cold
Hunting for Mr. Freeze’s Equipment in Arkham City. In the Hot and Cold side quest in Batman – Akrham City, you will find Harley Quinn in Steel Mill, all tied up. You have to talk to her. Then, you have to go search the Steel Mill for Mr. Freeze’s stolen equipment. Go to the east side of the room from the loading bay. Then open the blast door using the REC. Then, you open the hatch. There, you can find the Riddler Trophy. Grab it with the use of the Batclaw. When you do this, the Natural Selection (Extreme) challenge map will be unlocked.
Go to the elevator. Hack it so that the doors will open. Jump down. Using the REC, you can move up the elevator housing your enemies. Jump down using another elevator. Then, when you are down below, make the floor concrete blast apart using explosive gel. You can then pick up a Riddler Trophy. This will also unlock the Kidnapped Doctor character trophy. Note that you can also find a Riddler Trophy in one of the elevators.
You can enter that elevator from below to earn the Hell’s Gate (Extreme) challenge. Go up the boiler room entrance, taking down two guards in the process using Double Takedown. You are now free to go inside the boiler room.
Inside the boiler room, you will find both armed and unarmed opponents. Takedown one or two then disable the other armed ones. This way, you can fight fairly. Make sure you leave the Riddler henchman for last, at least if it is possible. This way, you can interrogate the guy. Blow the concrete wall to the right to get a Riddler Trophy. This one unlocks the Joker Thugs character trophy.
Go to the bin to find what you were looking for in the first place – Freeze technology. Here, you can find a Freeze Cluster Grenade. This weapon can freeze several enemies all at once. The enemies, believe it or not, can still attack even if they have been paralyzed by ice.