You can hire new captains by accumulating their fragments. You can obtain them either by researching captains in the Academy, or by using summoning scrolls in the Summoning circle.
Once you have enough fragments to unlock a new captain, follow the steps below to unlock and hire them.
  • Click on your hero avatar icon to open the hero and captain selection menu.

Click an empty captain slot

  • Whenever you accumulate enough fragments to unlock a new captain, that captain will be highlighted with a red dot in the captain selection menu to the right.

  • Now, click the captain's info.

  • In the "Hire a captain" section, click Summon to spend the fragments and hire the selected captain.

  • The hired captain will be automatically added to your selected free slot.

You can read more about the Summoning circle and captains' star levels.