Octo Valley (mode)

"Use your smarts and squid powers to save the Great Zapfish for the evil Octarian army in single-player story mode. Go get those Octojerks, bucko!"

- Splatoon's official website

Octo Valley is a single-player game mode in Splatoon. It involves the player donning the Hero Suit and venturing into Octo Valley to rescue Inkopolis' stolen Zapfish and defeat the Octarian menace.

Story
After the Great Zapfish, Inkopolis' primary power supply, is stolen, Cap'n Cuttlefish employs a Splatoon of Inklings to travel to the Octarians' secret underground base and retrieve it. Players assume the role of Agent 3 and traverse the treacherous landscape of Octo Valley in order to reclaim various lost Zapfish, Sunken Scrolls, and Power Eggs.

Gameplay
Octo Valley incorporates various puzzle mechanics and 3D-platforming elements. Gameplay has been compared to Turf War and Super Mario Galaxy, in the sense that it sees players splattering Ink to defeat enemies, transforming into squids, and traversing floating platforms. The Player's only available weapon in Octo Valley is the Hero Shot, a modified version of the Splattershot.

Mechanics

 * See more: Mechanics

There are many different mechanics that make an appearance in Octo Valley, such as Inkrails, Sponge Blocks, and Balloon Fish. These elements behave in various ways and are able to help or hinder players' progress.

Missions
Area 1
 * 1. Octotrooper Hideout
 * 2. Lair of the Octoballs
 * 3. Rise of the Octocopters
 * Boss 1: The Mighty Octostomp!

Area 2
 * 4. Gusher Gauntlet
 * 5. Floating Sponge Garden
 * 6. Propeller-Lift Playground
 * 7. Spreader Splatfest
 * 8. Octoling Invasion
 * 9. Unidentified Flying Object
 * Boss 2: The Dreaded Octonozzle!

Area 3
 * 10. Inkrail Skyscape
 * 11. Inkvisible Avenues
 * 12. Flooder Junkyard
 * 13. Shifting Splatforms
 * 14. Octoling Assault
 * 15. Undeniable Flying Object
 * Boss 3: The Rampaging Octowhirl!

Area 4
 * 16. Propeller-Lift Fortress
 * 17. Octosniper Ramparts
 * 18. Spinning Spreaders
 * 19. Tumbling Splatforms
 * 20. Octoling Uprising
 * 21. Unwelcome Flying Object
 * Boss 4: The Ravenous Octomaw!

Area 5
 * 22. Splat-Switch Revolution
 * 23. Spongy Observatory
 * 24. Pinwheel Power Plant
 * 25. Far-Flung Flooders
 * 26. Octoling Onslaught
 * 27. Unavoidable Flying Object
 * Boss 5 (Final): Enter the Octobot King!

Equipment
In Octo Valley, players don the Hero Suit and are equipped with a variety of weapons.

Hero Suit
The Hero Suit is a special outfit worn by Agent 3 and other members of Cap'n Cuttlefish's Splatoon. It appears to be largely gray with blue highlights and triangular-shaped earpieces. Many of the Hero Suit's specific functions are unknown.

Hero Shot
The Hero Shot is a modified version of the Splattershot, usable only in Octo Valley. It is able to be upgraded by spending Power Eggs.

Ink Tank
The Ink Tank holds Inklings' Ink content. It is depleted by using weapons and can be replenished by swimming in Ink of Inklings' color. The Ink Tank is able to be upgraded by spending Power Eggs.

Splat Bomb
Splat Bombs in Octo Valley behaves very similarly to the Splat Bombs found elsewhere in Inkopolis. They are pyramidal in shape with four transparent faces. Like the Hero Suit, they adopt a gray and light blue color scheme. When thrown, Splat Bombs explode after a short amount of time. This weapon is able to be upgraded by spending Power Eggs.

Burst Bomb
Burst Bombs in Octo Valley behaves very similarly to the Burst Bombs found elsewhere in Inkopolis. They are shaped like water balloons, and, like the Hero Suit, adopt a gray and light blue color scheme. When thrown, Burst Bombs explode immediately upon contact. This weapon is able to be upgraded by spending Power Eggs.

Seekers
Seekers in Octo Valey behave very similarly to the Seekers found elsewhere in Inkopolis. They appear to be small, mechanical devices that travel on the ground toward nearby enemies, leaving trails of Ink in their wake. Upon reaching an enemy or after traveling for a short period of time, they explode into a burst of Ink. Seekers are able to be upgraded by spending Power Eggs.

Armor
Armor can be found throughout Octo Valley. When wearing it, Inklings appear to be wearing a helmet and safety pads, and are able to take extra damage without getting hurt.

Special Weapons
Special Weapons can be found throughout Octo Valley in the form of Tuna Cans. Upon collecting a Tuna Can, a random Special Weapon is selected for immediate use.

Collectibles
Many types of collectibles can be found in Octo Valley.

Power Eggs
Power Eggs appear to be small, orange fish eggs that can be found throughout Octo Valley. They can be collected by killing enemies, destroying crates, and shooting or running near individual ones scattered around the environment. They are used for upgrading equipment.

Sunken Scrolls
Sunken Scrolls are rolled up pieces of paper that can be found in Octo Valley. They are long-lost drawings and other pieces of information that depict the history and lore of Inkopolis. One Sunken Scroll can be found in each level of Octo Valley.

Rewards
Playing through Octo Valley is not without its rewards. For defeating the final boss, the player is awarded a full Replica of the Hero Suit and a set of Octoling Gear. Also, the Sunken Scrolls found in each boss stage will unlock further weapons in Ammo Knights that are available for purchase once the appropriate level requirement is met.

Trivia

 * Boss battles feature a quiet but startling mechanical ambiance, accompanied with screeches and moans that sound similar to Zapfish cries. This usually cannot be heard due to music and sound effects during gameplay, but is easy to listen to before and after battles. The source of these eerie noises is unknown.