From Halopedia, the Halo wiki
The Elite Pathfinders appear on Attack on Sanctum and March on Stormbreak. On Attack on Sanctum, three Elite Pathfinders will spawn in the North Garage. They can wield Brute plasma rifles or Z-180 Scattershots. If they are killed on round one, the player will receive a Boss Takedown Medal. On March on Stormbreak, they appear in Type-54 Ghosts. They are easily killed by Z-520 splinter turrets.