Near the infirmary in Ostagar, there is a set of suspended cages. Inside one of them is a prisoner, with a guard standing nearby. Talking to the prisoner before heading into the Korcari Wilds triggers the side questThe Hungry Deserter.
The prisoner will beg for food and water and will explain that the nearby guard has some. If Alistair has previously been found and is in the party when speaking with the prisoner, then this quest can influence his Approval. Alternatively, the quest can be completed before speaking with Alistair to avoid any impact on approval.
The Warden can then:
Kill the prisoner without asking for any more details, generating Alistair disapproves (-5) .
Help the prisoner without asking for any more details, generating Alistair approves (+2) .
Ask why the prisoner is locked up.
Ask why the party should help.
The prisoner will offer the Key to Mages' Chest in return for help and explain that he stole it from a mage in the camp by getting him drunk, and was later caught wandering around the camp at night and locked up as it was assumed he was trying to desert. He swallowed the key, and it has since "come back into his possession."
To obtain the food and water from the guard, The Warden can:
Persuade the guard to forgo his lunch (requires 1 rank of Coercion).
Steal the food and water from the guard (requires Stealing).
Obtain food and water from the guard, generating Alistair approves (+1) .
Kill the prisoner, generating Alistair disapproves (-5) .
Steal the key from the prisoner.
The key opens the chest by the Magi Encampment, next to the tranquil mage. It cannot be used until returning to Ostagar after completing the Tainted Blood and The Grey Wardens' Cache quests in the Korcari Wilds. At that point, the tranquil mage will have moved: prior to this, attempting to open the chest will only prompt him to object.
If the key is not used before entering the Tower of Ishal, the quest will be marked as complete. However, the key can still be used during The Warden's Return to Ostagar (requires DLC), by which time the chest will contain the Corrupted Magister's Staff as well as the loot available during the main quest. If the key has already been used as part of this quest, then it will not be possible to open the Mages' Chest or obtain the Corrupted Magister's Staff during Return to Ostagar.
Note: If the Key to the Mages' Chest is not obtained as part of this quest, either because The Warden never spoke to the prisoner, or because The Warden fed the prisoner before finding out about the key, then the key can be looted from the prisoner's corpse during the Return to Ostagar. As noted below, there is the benefit of obtaining an additional item from the chest if it's opened later in the game.
Apprentice CowlApprentice CowlCloth helmet Circle towers are frequently drafty. The senior enchanters distribute these to the apprentices in the winter. Where they come by the cowls, however, is a mystery.
+5 mental resistance
Enchanter's Arming CapEnchanter's Arming CapCloth helmet Simple and effective, though certainly not standard equipment. Reserved for major Circle of Magi operations under full supervision of the Chantry, so much as they are aware.
+1 willpower +10 mental resistance
FlaskFlaskItem These simple glass containers are able to hold many compounds, even unstable ones.
Health PoulticeHealth PoulticeHerbalism A skilled herbalist has rendered a variety of medicinal ingredients into this soothing, restorative substance.
Lesser Injury KitLesser Injury KitHerbalism A kit containing bandages and other healing aids.
Lesser Spirit BalmLesser Spirit BalmHerbalism This balm has a soothing effect on the mind.
Be aware that if the key obtainable as part of this quest is used before the Battle for Ostagar, then there is no way to obtain the Corrupted Magister's Staff as part of the Return to Ostagar DLC If you want to solve the quest and also be able to come back later this mod can help.
If you obtain the key but do not use it before the Battle for Ostagar, then the quest will be marked as complete in the journal but the text will not reflect the actual steps taken.
If you do not talk to the guard, but rather steal the food/water, and give it to the prisoner. When you talk to the guard after he will say "You got your food and water! Now off with you!"
If you are too far away from the Prisoner (e.g. standing by the guard), sometimes the prisoner cannot be interacted with, even though the cursor shows him as clickable. Be sure to get right next to the cage so that you can interact with him.
If you persuade the guard to give you the food and water, give them to the prisoner and then steal from the guard, you will get another food and water but can do nothing with them. These will not take up inventory space as they are plot items, but they do cause visual clutter.