The deal is for Monday only and gets you a PC version of the game. You need a Bethesda.net account to redeem the offer and must have the Bethesda launcher downloaded to play.
Morrowind is the third installment in the Elder Scrolls series, the first of which (The Elder Scrolls: Arena) was released on March 25, 1994. The series characteristically offers an open fantasy world that allows users to explore freely instead of following a linear plot.
Bethesda is also offering other promotions as part of the celebration, including a sale on all Elder Scrolls titles and a free play week for The Elder Scrolls Online that starts Thursday and runs through April 4.