This dungeon opens at irregular times for an hour each time. There is no official announcement of the schedule. On the day of the event, the dungeon will be announced in the daily sign-in news. To find out your time, see Event Time Lookup.
This dungeon contains only three monsters from the Gold Dragon family, which provide experience for power-up fusion. Gold Dragon gives 1000EXP, High Gold Dragon gives 10000EXP, and King Gold Dragon gives 50000EXP, plus a 1.5x bonus for all if the base monster is a Light type. Moreover, while the common Gold Dragon only gives 1000EXP, it can be used to evolve Shiny Pengdra into Topaz Pengdra, which will give 30000EXP (45000EXP for Light type). See Pengdra Village.
Unlike Metal Dragons, this dungeon is also a great source of money. Killing a King will give 10000 coins, 5000 coins for a High and 1000 coins for a regular Gold Dragon. Every clear will get you 20000+ coins. The price for selling the gold dragons is also very high. Gold Dragons sell for 3000 coins, High Gold Dragons for 30000 coins, and King Gold Dragon for 300000 coins.