Skill tests are performed by rolling the Fate Die and comparing the outcome to the Skill Value for the type of skill being tested; the dieroll should be lower or equal to the Skill Value for the skill test to succeed.
There are two Skill Values: the Island Value and the Port Value. The skills are attributes of individual Crew member, found on their Crew Boards. If the event was triggered by using a specific Crew member, that Crew member's skill value is used. If multiple Crew members are involved, the player can choose which Crew member's skill value to use.
Skill test will sometimes happen as part of Resolving an Event, and are often called for by Sea Event cards, Expedition Cards and Denizen Cards.
Fate Die
The Fate Die is a ten-sided die with values from 0 to 9. It is used for Skill Tests, for determining the outcome of Looting a Shipwreck, gaining rewards for destroying enemies, and for various other randomized effects from cards and Port Board actions.
Various Traits can allow you or force you to reroll the Fate Die, or interact with the die rolls in other ways.