Here is the full list of all 50 The Chronicles of Narnia: Prince Caspian achievements worth 1,000 gamerscore.
Play 15 missions in co-op play.
Play 5 missions in co-op play.
Open ALL bonus chests in single or co-op play.
Open 75 bonus chests in single or co-op play.
Defeat 20 enemies while on horseback.
Rid Narnia of the Telmarines
Take control of the trees and destroy the Telmarine army.
Defeat Lord Glozelle in the Cistern.
Rescue Prince Caspian on the battlefield of Beruna.
Collapse the battlefield by destroying the support pillars.
Find a way into the secret cistern in Aslan's How.
Upgrade your health fully in the game.
Defeat Lord Gregoire in battle.
Successfully complete all areas in and around Aslan's How.
Defeat King Miraz in the combat ring.
Help Lucy escape on horseback from the How.
Defeat the White Witch.
Complete the Approach to Aslan's How area.
Open 50 bonus chests in single or co-op play.
Complete all of the areas in Miraz Castle Assault.
Rescue Cornelius from the stables in Miraz's Castle.
Reach King Miraz by scaling the castle terraces.
Battle through the courtyard to get to Peter.
Issue a reply to 100 Telmarine enemies in the battle.
Open the portcullis and let the Narnian army in.
Reach the control room to let the Narnian army in.
Defeat 25 enemies as Reepicheep.
Defeat 50 Telmarines as Trumpkin.
Complete all of the areas within Miraz's Castle Infiltration.
Rescue Edmund and Trumpkin from the bell tower.
Seek vengeance from 200 Telmarine soldiers.
Defeat 75 Telmarines as Susan.
Send 10 guards to sleep with Cornelius' sleep potions.
Rescue Cornelius from the dungeons of Miraz's Castle.
Defeat the sentries along the castle walls.
Use gryphons to take out the turret sentries.
Complete the entire Cair Paravel Ruins area.
Find a safe route through the woods.
Open 25 bonus chests in single or co-op play.
Rescue Trumpkin from the water.
Explore the treasure rooms and find the Pevensie's clothes and gifts.
Work through the cavern to find a grapple.
Escape Cair Paravel with Queen Susan's Horn.
Seal the doors and escape Cair Paravel.
Fend off the Telmarine ships.
Open 10 bonus chests in single or co-op play.
Defeat the archers that are threatening Cair Paravel.
Rescue Queen Susan's Horn from the throne room.
Use the giants to destroy the catapults in Cair Paravel.
Charge around as the centaur and take out 40 Telmarines.