Twelve-Winged Dark Seraphim
The phone is charging now. I estimate it will reach 100% in the next 10 chapters. Since normal phones usually reduce efficiency to conserve power at low battery, my guess is full charge will increase efficiency of a feature. Probably the dungeon one since that's the one with the most room for improvement. The download speed is pretty slow, so maybe that could be changed. Alternatively, maybe an entirely new function will be added to the phone.