The tabs (from left to right):
- Consumable (aka AP pots)
- Magic Light Stone
Magic Light Stone Edit
Magic light stone is an item you acquire from selling certain units in "Units" menu.
Selling rare units and above for character units (not all of them though) gives you this stone, starting from 3 stones for R rarity, 13 for SR, and up to 60-70 for UR (I still haven't got any SSR or UR, so I cannot confirm it myself)
This is the place where you exchange medals/event-related items for... Well, other items.
You can get premium tickets, upgrade tickets, and some chests from here.