Tributes are extra resources generated by the kingdoms a player has unlocked. These tributes can be earned once per hour, but only if the player collects income (by clicking their home kingdom).
A kingdom's tribute can yield extra Gold, Souls, and Glory; each kingdom has its own set of tribute amounts, i.e. Broken Spire's base tribute is 200 Gold and 8 Souls, while Adana's is 175 Gold and 2 Glory and 4 Souls.
In addition to the standard Gold, Souls and Glory, having multiple kingdoms provide tribute at once also gives Gold Keys and Gems (based on the number of kingdoms paying tribute).