The charts he stole from Sao Feng consist of concentric rings that slide alongside each other to change view and bring up strange writings.
"Over the edge over again."
When Will comments on how they can't be as accurate as modern charts, all he's given in return from Tai Huang is that they 'lead to more places'. He hopes it was worth losing Mal for. Will can't believe that the Captain is dead, and chooses to accept it when he's told he escaped. This voyage has yet to prove worth killing a friend for.
"Sunrise sets flash of green"
When challenged with this riddle, Barbossa gives Will one of his smug superior looks and has Gibbs explain some folklore about a green light flashing across the sky at sunset, signalling the return of a soul from the dead. It's helpful, Will reflects bitterly, that people shared with him something so pertinent to their mission. Barbossa, Gibbs, and for some reason Pintel all seem to revel in the dramatic telling of the situation, and Will finds himself missing the relative straightforwardness of sailing with Jack. That in itself is a depressing thought.
They sail up into the Arctic, so cold that one sailors breaks off his toe in his fingers. Will is so focused on the prize he hardly notices the cold, but it's to this that he ascribes Elizabeth's miserable huddling in a snow covered blanket, alongside Tonks. She doesn't talk to him at all, even when the weather becomes milder, focused as she is on rescuing Jack. Will attempts once for a conversation, but she just says she wants Jack back, so he acquiesces.
"Over the edge over again"
No one talks to Will at all in the long voyage, and he doesn't feel the need to talk to anyone. It's just Tia Dalma who approaches him, talking about the cost of what we want most. And just once he catches a glimpse of a locket she wears. One hauntingly familiar, from his time on another ship, when what he had to do seemed so much simpler.
It's in the dead of night, when Will is staring into the sea ahead, that he suddenly notices there's a lot less horizon than there had been before. Looking again, he sees that they're rapidly running out of sea, and all Barbossa can do is cackle insanely, babbling about being lost in order to find a place that can't be found.
When the current catches, Will takes charge of the crew, barking out orders to bring them around. It doesn't even occur to him that his orders won't be followed, even when Barbossa belays his commands, it's only the original Pearl crew which obey, racing to the side to look out ahead, from where is coming the most tremendous roar.
"Flash of green"
The rapidly approaching horizon is now mere yards away, and with the consuming current and deafening roar, it's obvious what it is: a gigantic oceanfall, stretching as far as anyone can see in all directions. Barbossa has led them, literally to the end of the world.
Now Elizabeth sees the urgency and joins Will and (his) Tai Huang's men in their attempts to turn around and save them, but it's too late, and the ship hits the edge side-on. It teeters precariously for a pregnant moment, in which Will looks around wildly to hold on to Elizabeth, but before he can reach her, the ship lurches over, tumbling into the cascade and shattering as the falling water batters it. Will loses her in the fall.
"Over the Edge"