#1) East of your hideout is the circus area and slightly northeast of that is a tower. This tower is the same one used to get on top of the circus tent in Juggling Act. The mask is found on a small tower that is part of the bigger tower.
#2) In the northwest corner of the first area you begin is a tavern, which has a spinning mug on its roof. The mask is found on one of the spire jumps on the roof.
#3) You will need Sir Galleth to acquire this mask. Go to the eastern section of the map and find the clock tower. There is a tall building just north of the clock tower that has a mask on its roof. Use Galleth's Catapult Crash technique to get to the roof.
#4) You will need Sir Galleth to acquire this mask. This mask is on a tower in the southeast corner of the map. About halfway up the tower, if you look around the corner, you will see a platform with the mask on it.
#5) You will need Sir Galleth to acquire this mask. Go to the tower at the southernmost point of the map. Climb all the way to the top, then jump down to the top platform. You'll see three breakable crates with the mask hidden in between them.
#6) This mask can be found in the Juggling Act mission. This mask is past the first set of falling trumpets. Once you hit the first moving target in the mission, break the red crate on the next platform to reveal a hidden barrel of arrows. Shoot the arrow at the barrel in the distance to reveal a target, then hit the target so you can walk over to the platform with the mask.
#7) This mask can be found in the Juggling Act mission. Immediately after the second set of falling trumpets, you'll be on a rope and have to climb down. Instead of doing that, climb all the way up to the top to find a platform with the mask on it.
#8) This mask can be found in the Mechanical Menace mission. As soon as you enter the cave and get to the base of the tower, don't start climbing it. Instead, go to the ledge on the right side and look down to find the mask on a lower platform.
#9) This mask can be found in the Shell Shocked Heart mission. This mask is located in the section where you play as Bentley. After you get past the first set of lasers in the very first room, continue until you pass a moving gear at the beginning of the second room. Immediately to the right of the gear is a bombable wall with the mask behind it.
#10) This mask can be found in the Shell Shocked Heart mission. Play through the mission until you hack and open the second door. In the proceeding hallway, you'll see some spinning gears on your left, as well as a crate in the corner. Throw a bomb to destroy the crate and reveal the mask.
#11) You will need to collect all 12 Treasures in this episode in order to unlock the arcade machine in the hideout. You'll be playing Alter Ego, or rather a "Super" version of it. Go through the first area and into the portal leading into the second section. In this area, stay on the south side of the screen and you'll eventually run into a portal not far from the beginning of the second section. You'll find the mask in plain sight in this portal.
