Guild Wars gas is used for retrying Guild Wars missions. The new option comes with a few rules:

• There is only 1 retry per mission attempt.
• The option retry is only available on the "Failed" mission screen, and it has to be played with the same survivors and equipment.
• The cost of each retry within one battle will scale up - each replay in the same battle will cost more than the previous.
• Retried missions have a 20% Victory Point penalty, in order to distinguish flawless performance from those that involved retries.