Of course, we are talking about the merchant!
The merchant is an infiltrator from the immune system, whose sole goal is to gain DNA profit in order to mutate.
What does he offer in return? An extensive selection of weapons and power-ups for Gaylord!
Of course, buying from the "Immuno Nation" machine or the "Power-ups" machine will always be cheaper, but the merchant lets you choose which items to buy, and you'll have both options in a single building.