Has anyone ever bought a Mysterious Old Box, what will you find when you open it? O.o

You equip it as a weapon and it gives you a random MC weapon. You can use it once per battle according to HQ.

Its not usable as far as i know. Its a battle weapon that when used in battle, gives you a Random MC Weapon(excluding the Potions) that you can use for the remainder of the battle the Box is returned to your Weapons.

I was also wondering about Blackheart Hollow. What do you need to buy something there? What kind of coin do you need? O.o

Wizard tokens. xD

Do you need a certain amount or does it restock periodically like the Token Shop?

it Randomly Restocks multiple times throughout the day. Like the token shop, Just much more frequent, normally only restocking one item at a time, Ad only 1 or 2 of that same item.

just try visiting the place every 20 minutes with the tokens in your items, You will see the item even if you have no tokens or not enough of them

Thank you very much, , you have been very helpful.