When your character wants to negotiate a price, the Game Master (GM) will ask you to make a Charisma (CHA) test. The difficulty of this test is determined by the GM and can vary depending on several factors. These factors include your party's reputation in the region, the relationship you have with the merchant, or even the rarity of the item you wish to purchase.
Example :
You visit a city where you are already recognized as local heroes. The GM considers this to give you a negotiating advantage. The difficulty of the negotiation test is therefore set at 12.
The character can negotiate with a merchant as long as he passes his Charisma test. On the first failure, the character will no longer be able to negotiate with this merchant until the next day.
Each success in the negotiation test allows you to determine the number of items or services that will benefit from the reduction, and will increase the total percentage of reduction on these items.