The One Up Kit can be used by its owner to upgrade a special building acquired in an earlier age to the subsequent age. Each kit can only be used once.
The kit was introduced during the 2016 Fall Event.
The One Up Kit can be obtained from the Rare Jade Relic during the Guild Expeditions. It can also be obtained as a reward for completing the 12th encounter of level II and the 12th encounter of level IV of the Guild Expeditions.
A player owns for example a Shrine of Knowledge obtained during the progressive era (and of course a One Up Kit). The player later finds out (for example during the postmodern era) that he or she wants to upgrade it to one age higher than the items current age. The player then picks the One Up Kit placed in the inventory and clicks the Shrine of Knowledge of interest (a star is highlighted above up-gradable buildings) and confirms the upgrade. After confirmation the building has the properties of the age one higher than the previous age rather than the properties of the age during which it was obtained. The One Up Kit is then consumed and removed from the game.