Propeller-Lift Fortress, also named Propeller Lift Fortress,(EU/OC)[a] is the sixteenth mission available in Octo Valley. It is the first mission of the fourth area after the third boss, The Rampaging Octowhirl!. The mission is named as such because of its heavy use of Propellers. It is also the first level to introduce Elite Octolings.
When first entering Area 4, Mission 16 can be found under the area. The player needs to fall down the large gap in Area #4. There should be two Inkrails (can be found to the left and right), and a Gusher. Take the Inkrail on the left, it will take the player to a Gusher and extra platforming. Mission 16 can be found on that platform.
Propeller-Lift Fortress features many Propellers. At the end of the stage, there is a battle against an Octoling and an Elite Octoling.
Collectibles
Sunken Scroll
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Before the Great Turf War, there were amicable relations between the Inklings and the Octarians. They couldn't have dreamed that rising sea levels would force them to battle fiercely over the remaining territory.
Location: At the third checkpoint on a floating platform above the pool of water. After hitting the checkpoint, use the turret to hit the fan, bringing the platform over to you. As you defeat the enemies, keep note of the taller portion of the wall to the left. Ink a trail up that rather than the main wall when you reach the end of the pool. Climb up it, spray the ground, and turn around. Using the ink you sprayed, jump over to the platform as a squid and get the scroll within the crate. If you went up the short part of the wall, do not worry. You can still wait for the fan to move the platform out so you can try again.
Armor
Propeller-Lift Fortress contains a grand total of five pieces of armor.
Propeller-Lift Fortress Beginning Area-Armor #1
Armor 1 location: Before going into the area with the Octotrooper, make sure the platforms are moved far enough to reach the first armor. It can also be done by jumping in squid form to reach the lone platform. Can be found in the beginning.
Propeller-Lift Fortress Checkpoints 1 and 2-Armor #2
Armor 2 location: There are two small crates on the right side of the wall which advances Agent 3 to the next checkpoint. Destroy the top crate, which will reveal armor. Can be found in checkpoint 1.
Propeller-Lift Fortress Checkpoints 1 and 2-Armor #3
Armor 3 location: One of the crates away from the group of Octobombers wields armor inside. Can be found in checkpoint 2.
Propeller-Lift Fortress Checkpoints 1 and 2-Armor #4
Armor 4 location: Going into the area with two Octotroopers, there is armor on one of the platforms that will rise when the Propeller-Life is being shot at. It can be picked up even if the platform is elevated. Can be found in checkpoint 2.
Propeller-Lift Fortress Final Checkpoint-Armor #5
Armor 5 location: During a duel with the Octoling, the last armor can be found on the right side of the platform. Break the two crates and the armor will appear. Can be found in the last checkpoint.
Special weapon
Location: The Bubbler can be found in the last checkpoint. It can be found on the left platform of the Propeller-Lift's platforms. It will be helpful to fight against the two Octolings.