LOX was a substance that was stored in pressure tanks in the Azzameen family's cargo fields. Some time after the Battle of Hoth, the pirate cargo ferry Raider attempted to steal a pressure tank containing LOX from the Azzameens, but was stopped by training pilot Ace Azzameen, his sister Aeron, and Azzameen droid MK-09.
Though the exact substance is not clarified in Star Wars: X-Wing Alliance, "LOX" is a standard abbreviation for liquid oxygen. Lox could also refer to a type of salted fish.