The Shrine, once restored in the Bastion, allows you to activate Idols. Idols are modifiers that increase the game's difficulty in various ways, such as making enemies stronger, faster, or more numerous. In return for this increased challenge, you gain bonus experience and Fragments from defeated enemies.
Activating Idols is an excellent way to farm currency and experience, especially if you're looking to fully upgrade all your weapons and Secret Skills. It also provides a significant challenge for players seeking a harder experience. You can activate as many Idols as you wish, but be warned: the game can become extremely difficult with multiple Idols active. Experiment with different combinations to find your preferred level of challenge.