Your castle in Yllian is the center of a lot of things and helps you get stronger in the game. Upgrading it makes it more powerful in terms of the things it can offer such as meeting companions, training companions, gathering resources, and researching spells. While you don’t have to do anything besides playing the game and progressing in the story to unlock the upgrades, you do need to revisit the castle to check if there are upgrades available.
When an upgrade becomes available, you will be able to see it in the castle menu when you interact with it. The upgrade button will be greyed out when the upgrade is not available. There are four tiers that you can upgrade the castle to.
When you complete a region in the game, come back to the castle and check if an upgrade has unlocked. Each upgrade will allow you to get more powerful companions to join your quest. The castle upgrade will also boost Avyanna’s leadership level.
Each upgrade comes at a cost such as gold, wood, iron, and divine essence. While the rest of the resources are easy to find, you will need to dismantle rare or higher quality equipment to get the divine essence.