Po-Koro Chisel

The Po-Koro Chisel was a golden-color carving tool that had belonged to Turaga Onewa.

History
At some point in time, Turaga Onewa came across the Po-Koro Chisel and used as a carving tool. He was unaware that it was actually a "key" to unlocking the portal leading from or to the Bohrok nests.

Mata Nui Online Game
Turaga Onewa rewarded Takua with the chisel when he discovered the infected Comet Balls were the ones causing "The Madness" in Po-Koro and helped Toa Mata Pohatu with defeating the Nui-Jaga while also ending the threat and the production of the infected Comet Balls.

When Takua returned to Ga-Koro, he showed the chisel to Turaga Nokama as proof of his accomplishments in Po-Koro. He was then given the Book of Chronicles from her.

Much later in the game, Takua quickly inserted the chisel into a golden-color orb which activated an energy shield bubble around him and took him up through the portal and then tossed him onto Ta-Wahi Beach.

Trivia

 * The "head" of the chisel looks similar to Turaga Onewa's hammer.