Octopus Cave

Octopus Hunting Stick (6442) can be exchanged for some Nyangvine Fruit (6909) from the Vending Machine in Malangdo.

You'll be warped into a cave with 4 warp portals. Enter one of the portal and walk until the end of the tunnel. There is no need to kill everything and the order of the portals don't matter.
Kill the Octopus Leg.
After killing 4 Legs, you'll be teleported back. Prepare for the boss fight.
Crossing the new warp in the north you'll reach the boss room. There will be the Giant Octopus, several Octopus Legs and Octopuses. Kill the MVP.

Monster	Level	HP	Size/Race/Element	Valuable Drop
Hydra (1068)	34	854	Small / Plant / Water 2	Hydra Card (4035)
Stapo (1784)	95	8,805	Small / Formless / Earth 2	Cute Grass Necklace [1] (28381) Stapo Card (4424)
Deep Sea Marse (2175)	95	120,000	Small / Fish / Water 2	Poor Coin Bag (12615)
Octopus (2192)	90	6,000	Small / Fish / Water 2	Octopus Card (4533)
Octopus Leg (2193)	95	500,000	Small / Fish / Water 2	Poor Coin Bag (12615)
Giant Octopus (2194) (MVP)	95	500,000	Large / Fish / Water 2	B Grade Coin Bag (12618) Normal Coin Bag (12614) Advanced Weapon Box (12818) Poor Coin Bag (12615) [MVP] Giant Octopus Card (4534)

Name	Description
Hydra Card (4035)	ItemID: 4035 _______________________ Increases Physical Damage against Demi-Human race by 20%. _______________________ Type: Card Compound on: Weapon Weight: 1
Stapo Card (4424)	ItemID: 4424 _______________________ Enables use of Find Stone and Throw Stone skills. _______________________ Type: Card Compound on: Accessory Weight: 1
Octopus Card (4533)	ItemID: 4533 _______________________ Random chance to inflict Blind status on the target when dealing magical damage. _______________________ Type: Card Compound on: Weapon Weight: 1
[MVP] Giant Octopus Card (4534)	ItemID: 4534 _______________________ MaxHP +12% _______________________ Enables the use of Level 5 Waterball. _______________________ Type: Card Compound on: Armor Weight: 1