Erstin Deez was a human male who served in the Imperial Royal Guard, with the rank of sergeant and later major. Deez accompanied Galactic Emperor Sheev Palpatine and Darth Vader to Ryloth aboard the Star Destroyer Perilous, when the group became the target of the Free Ryloth Movement. Although the other guardsmen were killed, Deez, the Emperor, and Vader all survived. Years later, Deez was assigned to the throne room in the Imperial Palace alongside a cadre of other guardsmen. When the Emperor and Grand Vizier Mas Amedda entered the room, Deez and all other guardsmen were poisoned and killed.
By the Imperial Era, Erstin Deez served as a sergeant in the Royal Guard of Galactic Emperor Sheev Palpatine. He accompanied the Emperor and his apprentice Darth Vader on a visit to the planet Ryloth in the Star Destroyer Perilous. When the Perilous was attacked and destroyed above Ryloth by the rebellious Free Ryloth Movement, Deez evacuated with the Emperor and Vader in a shuttle, but their craft crash-landed on Ryloth, leaving them stranded in the wilderness. Deez, Vader, Palpatine and a captain of the Royal Guard made their way across the terrain searching for civilization, encountering a nest of native lyleks which they destroyed at the cost of the captain's life. They then came upon a Twi'lek village, where they were welcomed and rested before being attacked by Free Ryloth movement members. The trio fought off the attackers, aided by Imperial reinforcements who soon arrived to collect them.
Between 3 ABY and 4 ABY, Deez served as an Imperial officer with the rank of major, as well as still part of the Royal Guard. The assassin Ochi, acting on the orders of Lady Qi'ra of Crimson Dawn, traveled to Coruscant where he acquired a number of poisons, one of which he used to infect Deez in an attempt to take out the members of Palpatine's guard. Sometime later, when Deez and the other guards stood before Palpatine and Grand Vizier Mas Amedda in Palpatine's throne room, they all suddenly dropped dead, to the surprise of Amedda.
Erstin Deez first appeared in the 2015 novel Lords of the Sith, written by Paul S. Kemp. Deez was later depicted in the second issue of the comic miniseries Star Wars: Crimson Reign, written by Charles Soule, and published by Marvel Comics on February 2, 2022. Soule clarified that the characters were the same on Twitter.