When you place a Monster’s Like near them, their Happiness will increase up to a maximum of 100%. Monsters produce Currency faster as their Happiness increases. You can see a Monster’s Likes in its Info menu. Each Monster has a hidden Like for you to discover!

The Unity Tree Structure, unlocked at Level 16, has the power to broadcast the Likes’ Happiness all around the Island. That means once you get a Unity Tree you can place a Monster’s Likes anywhere on the Island (including inside the Storage Structure)!