The Clock Tower of Eternity is a time-limited dungeon within Fort Solgres.
Unlocking the Clock Tower of Eternity requires using an entry token, which allows access for up to 30 minutes.
There is a limit of 12 fights per unlock, but the fights are repeatable. Each fight grants 1 - 2 Super Awakening Coins per fight, with additional rewards granted for finishing the fight multiple times within the progress bar. Additional rewards are also given for finishing all of the three stages for the first time.
A variety of teams can be used, but the optimal way to farm within the time limit is to manually battle the first stage and exit if the first phase doesn't drop a chest. This method should be able to result in at least 24 Super Awakening Coins per 12-fight run.