He leads his own faction of evil wizards, and his own agenda is a lot more important to him than Ranrok's rebellion.

Source: https://www.cbr.com/harry-potter-hogwarts-legacy-all-main-characters/

The Carted Away side quest tasks Hogwarts Legacy players with rescuing a distraught Goblin's enchanted carts from some of Ranrok's loyalists.

Source: https://gamerant.com/hogwarts-legacy-how-to-complete-carted-away-side-quest-guide/

Unfortunately, not much else is known about Loyalist Sentinels and what role they play in Ranrok's army.

Source: https://gamerant.com/hogwarts-legacy-how-to-beat-loyalist-sentinels/