The gate to the slave pen is only held shut with a simple latch. The slaves inside are manacled at the hands and feet, attached to a long chain staked in the ground. A quick search of the bodies reveals a key on a necklace around the sorcerer's neck, and an assortment of other items.
loot
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3x scale mail
1x chain shirt
1x hide shirt
1 longsword
1 medium wooden shield
1 spear
1 shortbow
20 arrows
1 scizore
1 battered blunderbuss
1 rapier
350 gp
1 ring (spellcraft DC 20 to identify)
4 potions (perception DC 17 to identify)