One of two stores (the other being the Monster Ranch) available in Adventure High.
Molly works here by default, but it's possible to enslave her and force her to give you items for free. Abusing this causes her to get fired, at which point Eric takes over and you no longer get free items.
It's unlocked by reaching the fourth floor of the Dungeon for the first time.
The first time you come there, speak to Molly and she'll ask why she have rarely seen you there before.
The Protagonist admits to having a poor family and as such never really bothered going there. Molly gives you a Converter which makes gives you access to Gems. Each time you finish a battle (or enemies escape), you gain 10% of the EXP in Gems (so if you got 700 EXP, you get 70 Gems).