The game starts at the entrance of Marceline’s cave with Finn looking for Jake. BMO can be seen walking few steps a head and behind him is a small house which belongs to Marceline.
The tutorial starts explaining how to move and look around. Once you move and reach BMO, the tutorial explains how to interact with NPCs. BMO will tell you to talk to Marceline, who can be found at her house.
Marceline will tell you about some noise outside her house. Talking to her again offers the option of asking her about the wooden planks blocking the way to the western part of the cave and she will suggest a hammer as a tool to remove them.
BMO has a hammer (for some reason) but would only offer it as a reward for defeating him in the “cheapest mini-game ever”, hide and seek. He isn’t that good at it.
Near BMO’s last hiding spot is a hole in the wall opposite of a path blocked by wooden planks. The hole is a peeping hole showing an unreachable place where a strange horse like creature can be seen. If stared at long enough (until its pupils enlarge) it, the Whacked-Out With Poo Brain Horse will start to follow you around. It will change its location every time it is off screen.
A weapon is needed to clear the path here (the hammer won’t do).
Once the hammer is obtained, the western part of the cave can be accessed.
The hammer is used at the entrance to the western chamber at the main chamber.
Next to the entrance to the right and above a small cliff is a green metallic door. It can be reached by jumping on the horse and BMO might have an idea on how to open it. There is also a small rock near the mechanical door which is a part of the door puzzle, but this is for later.
Straight ahead above a cliff is a glowing grated gate. Below it and on the face of the cliff are markings of circles, arrows and a bomb; take note of them for the future.
To the left is a path blocked with stones, examining it will reveal the possibility of using a bomb to clear it. Take a second note of the markings on the cliff next to the blocked path.
To the right is a long outstretch (The Sword Path) with a sword at the end. If you go for the sword fireballs will start to rush towards to test your worthiness of the sword, they will not kill you but will slow you down. Once you clear the infernal traffic Finn will get a sword and the ability to fight.
The tutorial will explain combat with a number of worms to get you warmed up. You will notice the bubbles dropped from the defeated worms and their counter above your health bar, they aren’t important at the moment.
Also, take note of a possible path above near the start of the sword path for the future.
You now can break the planks near the peeping hole at the main chamber.
Don’t forget to talk to BMO about the mechanical door on your way there.
Once back at the planks that can be broken with few hits, a narrow hallway will lead to an opening overlooking Marceline’s house. You can see a glowing star over a platform on the other side of the cave and something stuck at the top of the house.
There are also platforms on the right which can be used as a shortcut to the other side of the cave.
At the end of the hallway is the entrance to the maze. The tutorial will suggest talking to Marceline about it, but if you remember the markings in the western chamber then you can figure your way through it (there is a puzzle solution section at the end of this walkthrough in case you don’t).
Beyond the maze is the vertical chamber where the tutorial will explain jumping!
After some basic platforming you will reach an area where some worms will challenge your adventuring spirit.
There is a ladder that leads to an area above. A glowing star that would grant Finn the dash ability is waiting there.
The tutorial ends there after teaching you how to use the new ability and reminding you of the bomb above you. Drop to the area where you fought the worms and there is a rock the floats upwards but can only be reached with a dash. Go up and jump across to get the bomb.
Once outside the maze, try the platforms near the opening (if you haven’t already) and see if you can notice something interesting on them. If you do, note it down for the future.
On your way back to the western chamber, see if you can get the thing on top of the house. The horse can be useful for that if you can get it to go near the house.
The hall beyond the blown up stones have some worms and one Fruit Witch and once defeated three pillars will shoot up and can be climbed to the upper part of the chamber.
The large pathway nearest to the pillars leads to the beach and is not a current priority. Near the entrance of the hall are two paths, the one to the right leads to a platform overlooking the house and has the glowing star that we saw from the other side. Once the air dash is obtained with this star the beach becomes the next station.
The beach has some drift wood floating in front of it leading to a three land masses in the water. The first land mass has some worms and a couple of Fruit Witches while the second has a giant sea monster.
Defeating the monster and using its body to reach the third land mass that has Breakfast Princess waiting on it. The princess was stranded somewhere and has walked a long distance to find herself in the ocean?
Helping her reach the beach earns Finn a key. The princess leaves to pull a “prank” on Marceline.
Leave the beach then come back to find that she is back at the beach. Ask her “what now?” then get a potion if you have 250 “rainbow bubbles” (the ones that drop from defeated monsters).
Back to the western chamber and up to the left path of the upper part. You will find the grating gate on the left with mist blowing from beyond it. It is the room that is opened by the key you just got.
The room is the camp of the Ice King and has two notes in it, on on the couch to the right detailing the plans of the Ice King and another on the table to the far left giving a hint to reach the alternative dimension. You will come back for this later though.
As soon as you leave the room, there are two platforms on the left, one above the arch leading to the sword path and another bringing you closer to the mechanical door. Get on the one above the sword path and then jump air dash to another platform beyond it to reach an exit leading to a stone bridge above the lake of the main chamber.
At the end of the bridge is a metallic cylinder with a Phil face at its end. Examine the face then jump down to pay Marceline a visit if you want to see how she was pranked.
Asking BMO about the metallic face will give you half the info you need to activate it. The other half is on the shortcut platforms above.
Go back to the metallic face and activate its puzzle, it isn’t a hard one to solve (the solution is at the end of this walkthrough in case you can’t solve it). Succeeding earns Finn a “square thingy” that BMO will need to open the mechanical door. BMO will also need you to tie the rope found at the top of Marceline’s house to the rock next to the mechanical door so he can get to it.
With the square thingy in Finn’s possession and the rope set up, BMO will open the mechanical door when asked about it.
Now at the room behind the mechanical door is Princess Bubblegum and the machine that lets you view character models. Asking her about Jake will reveal that the he was last seen with the horse! Finn decides that it is the Ice King and plans to face him in a final showdown.
Asking the princess about the machine enough times will allow Finn to use it.
Back to the Ice King camp to find that the boss has not been made yet and the Ice King in his horse custom is standing there complaining about not getting a character model. He also tells you that he fixed the light switch.
Ask Ice King to follow you and then go to the far right of the room, the light switch is next to the TV and will allow you to see the hidden images in the posters on the walls.
The hidden images of the princesses (and only the princesses) contain the solution to the second path of the maze, the one leading to the alternative dimension. Ice King’s note on the table to the left has the hint to the solution (and if you can’t find the solution, it is at the end of this walkthrough).
Through the maze and into the alternative dimension, you get to play Fionna.
Leave the maze then go back in using the normal path to get to the vertical chamber and platform to where the bomb was in Finn’s dimension to find an outfit for Finn.
You will also find the Demon Blood Sword at the same place as the normal sword in Finn’s dimension and face the stronger sea monster at the beach.
Defeating the sea monster will allow you to reach a box containing a new outfit for Fionna.
You can meet the male versions of Marceline and Princess Bubblegum, Marshall Lee and Prince Gumball respectively. The Ice Queen is also stuck in a horse custom in this dimension and can be found at the peeping hole then in the Ice King Camp.