Redanian Foot Soldier is a 1-strength Close Combat unit with no ability. It’s a basic filler card, mostly there to help you reach the 22 units a deck needs.
Two copies exist, and both come in the Northern Realms starter deck Geralt receives when he learns gwent in White Orchard. You don’t have to buy or win anything.
Once you collect stronger units, these are usually the first cards to swap out. Until then, remember that a Northern Realms deck draws an extra card whenever it wins a round, so even weak filler units can help you take that first round.
