Dungeons are a key source of XP and essential resources. You get two free entries per day, and VIPs can purchase extra attempts depending on their level.
Among the four dungeons, Secular Training and Ghastly Treasure mainly feature mobs and drop the most needed resources: XP and Coins. Beast Villa and Penglai Temple feature a single boss, mainly dropping materials for upgrading Celestial Ghosts and Pets. Let's take Secular Training as an example for efficient clearing tips.
After entering, you get 5 seconds to prepare. Pay attention to the icons at the top-right: Protect, Inspire, and Efficiency. These may look small, but they can double or triple your rewards!
Protect: Boosts XP gain by 50%. It costs 558 Bound Ingots but lasts a whole month. Definitely worth buying if you have enough Bound Ingots.
Inspire: Increases damage dealt, up to 100%. Use coins and Ingots to boost this. Maxing the coin side is a must, and spend Ingots if available—levels are everything!
Efficiency: Exclusive to Secular Training. Here, you can use XP potions—up to 200% boost. At minimum, use a 100% potion to maximize returns from this limited-run dungeon.