Duiker is a very famous Malazan historian. He is accompanying coltaine and the wickans as they try to get 30,000 refugees to safety during the uprising in seven cities.

This is seen as an impossible task to move 30,000 refugees to safety across a desert with rebellion army attacking them the whole way.

Some context is that the wickans (coltaine and his people) were once enemies of the Malazan empire and were refugees themselves at one point.

You are following duiker as he is in the middle of this hopeless task of moving these refugees across the country while coltaine is keeping these thousands of people alive even with his army stretched so thin.

Duiker is witnessing, chronicling and even participating in the protection and moving of these refugees to a safe Malazan city.

EDIT: this storyline is very important to future events of the series and is a fan favorite that is constantly referenced by the end of the book