If a player does not choose within the five seconds, the game will automatically give you the first chest, starting from the left and ending at the right.
In Kounat's Collapse and Hero Dungeons, an instant reward pops up instead of treasure chests.
In Zeruel Border and Zeruel, chest can contain Gems among with the usual items.
After a Champion Mode dungeon run, players are able to open a special chest instead of a generic one. Special chests contain more GP than the general ones, and one of the four chests usually contains precious pearls.