Obtain the Key of Serpentis, then play level 10-7, "Jokulkyrkja", in Antarctica. Jump on the platform with the strange serpent symbol and it will lower into a Boss fight. Defeat the boss by throwing knives at the crystals on the ceiling in order to break each section of the dragon platform you are riding on. After the Boss has been defeated you will unlock Antarctica for all characters, Jim Hawkins, and the alternate ending.
Antarctica Temple
Complete all Akumpa Ruins levels. To unlock Antarctica Temple for all characters, view the True ending.
Change character's color
Collect four golden skulls.
Commander Video
Collect 6 golden skulls.
Counseil's Duty Free Shop
Collect twelve Golden Skulls.
Key of Serpentis
Play level 2-1, "Rush into the Ruin", at the Ukampa Temple. One the right side of the exit is a unique block with a key symbol. Remove the key block and enter the new area to the right of the exit. Note: Removing the block may require all Golden Skulls. The Key of Serpentis can be found in the center of the temple area.
Lost Levels mode
Collect ten Golden Skulls.
Pokemon reference
Complete World 1 and watch the video sequence. Aban will talk about the temple of Poko-mum and refer to it as "Pocket Monster", which is the Japanese title for the Pokemon series of games.
Tower of Nanar cooperative mode
Collect 5 golden skulls.
Various Characters
Complete the indicated task to unlock the corresponding character.
Character
How to unlock
Commander Video
Collect eight Golden Skulls.
Curly Brace
Collect thirty Golden Skulls.
El Testigo
Collect twenty six Golden Skulls.
Jim Hawkins
View the True ending.
Juni
Collect eighteen Golden Skulls.
President Thompson
Collect twenty Golden Skulls.
Sugimoto
Collect sixteen Golden Skulls.
Tina Hawkins
Complete Ukampa Ruins.
Zombie
Collect twenty three Golden Skulls.
Various Trophies
Complete the following tasks to unlock Vita trophy rewards.
Trophy
How to unlock
Collector (Gold)
Unlock every character and costume.
Golden Boy (Silver)
Complete the Golden Temple.
Headhunter (Silver)
Collect all golden skulls.
Lost and Found (Bronze)
Complete the Lost Levels.
Serpentine (Bronze)
Find the Key of Serpentis.
Speed Runner (Silver)
Complete every stage of the main game as Aban Hawkins with a cumulative time of less than 30 minutes.
