Some tiles have negative effects, such as the FATIGUE tile, which increases all Energy costs.
Others only have story-related effects, such as the DREAM tile. This tile shows the player short cutscenes while they’re asleep.
NPCs can be found in certain locations to trade with for tiles, or simply to provide story context.
The Fortress location contains a Library where players can learn the lore of the world. This also indirectly explains the abilities granted by the tiles.
Clues leading to the specific tiles that are required to unlock the Ancient Door can be found here.