A calamity is set to emerge from the abyss at the end of the year. You must prepare for it within a year while defending and descending. Fortunately, with the power of reseting time, the clock isn't ticking as loudly as it seems.
This is an incremental tower defense game where you manage the tasks for your personnel, gather resources, recruit and nurture 36 unique characters, and dig deeper into more floors for more mechanics.
Having your base breached doesn't mean game over, but time will be reset for 1 day, with some progress retained. Reset time to gain record for permanent upgrades. Continue this loop till you've prepared sufficiently to solve the problem, breaking free form this endless year.