first you have to get doubloons from the ocean and buy a war ship, then, you have to deafeat captain crawfish. after that you go to the governor and give him the map. in exchange, he will give you the shovel and keys. then you go to skullduggery and get the treasure.
There is no key card in skullduggery island.
do you mean skullduggery??
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skullduggery island!
You don't!
dragon cove
5128904
solve the mystery
The combo is 312.
a map piece
under the bridge on skullduggery
you can get one on skullduggery island