The Magi Sentinels (a single member was called a Magus Sentinel) comprised a group of robed figures. These individuals served to protect the ruler of Onderon during the era of the Freedon Nadd Uprising which occurred circa 3998 BBY. They acted as guards for King Ommin's underground stronghold. It was this location to which Satal and Aleema Keto traveled, seeking Ommin's assistance in deciphering a Sith spellbook they had acquired by theft.
By the Clone Wars, which took place in 22 BBY, the Magi Sentinels had vanished from the scene. However, Zeta Magnus, a genetic anomaly, was seen wearing attire reminiscent of their garments.
Later on, Darth Sidious created the Imperial Sentinels to guard his Dark Side Adepts. These Imperial Sentinels were equipped with cloaks and armor that bore a resemblance to the gear of both the Magi Sentinels and Zeta Magnus.
The Magi Sentinels of Onderon made their debut appearance in Star Wars: Tales of the Jedi – The Freedon Nadd Uprising. This was a comic book sub-series from 1994 within the larger Tales of the Jedi comic series, and it was penned by Tom Veitch. However, it was Abel G. Peña who formally identified them as such in the eNovella SkyeWalkers: A Clone Wars Story. This novella was written across the years 2008 to 2011 but was not published until 2015. Peña interpreted the visual similarities between the unnamed guards in The Freedon Nadd Uprising and the Imperial Sentinels from Veitch's Star Wars: Dark Empire as intentional. He therefore clarified the connection by describing Zeta Magnus's similar attire.