Well this is the Blacksmith. Gems are the name of the game in this store.
So lets begin: all of the gems you collect via Clan Mines, Non-player characters (NPC's) and in many other places. These gems can be used here to upgrade weapons for a small cost, and if you enter the back room with Cassandra, Rawr! she'll upgrade your armour for the cost of 3 master crystals 200,000 gold.
Game resources- Check here for how each gem will affect your weapon/armour.