Spoiler Alert!
This page contains content that can spoil the game! We encourage you to discover this content for yourself before reading further.
Chests will contain a relic, and can spawn in random encounters. In addition, the middle row of each area's map will have a chest.
Destroying all the bombs in a chest's board can yield a second relic, once per area. This is, however, extremely difficult. Using Enhanced Gunpowder and Short Fuse can be extremely helpful, should you wish to try.
While not a common situation, the bonus chest is earned by destroying 5 bombs total, not just the specific bombs in the board. Creating a bomb with a relic like Powder Collector and destroying it will count for the bonus chest.
