In the Midst of Withdrawing

Players who beat an event map from the Spring of 2013 event would no longer have access to said map once it was beaten. In the example above, this player beat Spring 2013 Event Map 2 which is now greyed out and no longer has access.

In the Midst of Withdrawing is an Event Only Mechanic that was introduced only during the Spring 2013 Event. It was the only time this mechanic was introduced and to this very has not been seen or is likely to never return.

Introduction

In the Midst of Withdrawing was a mechanic that would basically let players go about event maps and battle against the boss fleets on the map. Once the boss fleet had been successfully defeated, the map in which you defeated said Abyssal Boss would since then be greyed out and locked out for the remainder of the event. Players could no longer return to the said event map that they completed with the exception of the 4th and final map on the event from the Spring of 2013.

Conclusion

The likely conclusion why this event mechanic never returned was because the dev team was experimenting with event maps at the time and since this event map was more of an "early testing ground" for the future events to come they were likely to change things up following the first event map once they found a better conclusion to how to construct an event map. As of current, event maps have been used a farming grounds to collect rare kanmusu which has become a major tend in the events following Spring of 2013.