Allies, Blood Sport and The Uninvited are three missions as part of the Gondor storyline in Middle-earth: Shadow of War, which unlock in sequence.
If you are interested in completing other missions in the game, our Shadow of War guide and walkthrough can help.
Prerequisite: Complete Ring of Power.
Reward: 7575 XP, 900 Mirian
Rescue the Gondorians: The same procedure as your previous rescue mission.
Reach the Cave / Rescue the Gondorians: Once you've rescued four of them you'll be interrupted.
Defeat the Captain: Ûbkûk the Endless is your opponent for this fight. Start by unseating him from his Caragor, then concentrate on hitting him with a Stun and following up with a flurry of blows. Baranor lends his assistance, and between the two of you he should succumb without too much bother.
He probably outlevels you at the moment so can't be recruited, so either kill him outright or shame him so you can collect him later.
Rescue the Final Gondorian.
Prerequisite: Complete Allies.
Reward: 8675 XP, 930 Mirian
Defeat the Caragor. Exactly as straightforward as it sounds.
Defeat the Ologs: Two to tackle, but you have backup.
Defeat the Pit Fighters: An all-out brawl, but nothing punishing.
Defeat the Captain: Kûga Fast Feet is, as his name suggests, fairly nimble. He's immune to ranged weapons so you'll need to fight head on, but he's vulnerable to being stunned so once you've got him on the ropes he's easy to manage.
Need more help? Our Shadow of War guide and walkthrough gives you an overview of everything you need, but if you need something in particular, we have pages on Shadow of War Fortress Sieges, how to earn Mirian in Shadow of War, a guide for how to import your Nemesis and Follower to Shadow of War, collectibles guides like how to get all Shadow of War Legendary Armour and Weapons sets, a list of Lost Artifacts and Web of Fate locations, and Ithildin Door poem solutions and Shadows of the Past, along with how to grind XP in Shadow of War to power through the tricky Shadow Wars endgame and get the true ending. Finally, there's Shadow of War's army building explained and the best skills and how to earn Skill Points.
Prerequisite: Complete Blood Sport.
Reward: 9780 XP, 930 Mirian, and a Gondorian Artifact.
Poison the Grog Barrels: You need to get five, but there are at least a dozen scattered around so try and pick ones that won't immediately draw attention.
Hide in the Bushes and Wait for the Enemy Captain: He's in no rush to turn up, so be patient.
Defeat the Captain: Ishmoz Graug Catcher is vulnerable to explosions, and as luck would have it Grog Barrels explode quite violently when shot, so try and draw him near to one and then set it off. Once he's on fire he should be an easy target!