Thief enemy line

Thieves, Bandits, and Brigands are encountered several times in Golden Sun and Golden Sun: The Lost Age. Although human, game play wise they function exactly as any monster line. The only difference is that they are not engaged by a random encounter. Often, they operate in groups, and in secret.

Role in the Story
In Golden Sun, when the player first enters the town of Vault it is currently being inflicted with a series of thefts. Isaac and the party found the hideout of the thieves and confront them leading to a battle with the gang which consisted of three men: 2 Thieves and a Bandit. Although imprisoned, the gang later escaped during the course of the game.

If the player transferred data from Golden Sun then the Vault thieves will be encountered again in The Lost Age. As Felix's party leaves Madra, the gang appears when they learn he knows Isaac. Hoping to get revenge, they attack Felix's party. When defeated, the Vault gang retreats and decide to leave Isaac alone.

Story line wise the Brigands have no known relation to the Vault thieves. They are based in the town of Lunpa. Lead by Dodonpa, this gang was powerful, having control of a whole town and a massive fortress complex. Red Brigands guard the area and attack the party on sight (unlike the green variety which must be avoided), they are generally unavoidable.

Lunpa the Righteous Thief is a notable exception from typical thieves.

Thief
The Vault Thieves consist of three members, two being actual thief monsters. Each of the thieves have 110 HP, 42 Attack, 5 Defense, 9 Agility, and 1 Luck and balanced resistances to all four elements. They can only attack physically, defend, or use a herb. When defeated, they yield 15 EXP and 32 coins each. When encountered in The Lost Age, they each have 212 HP, 196 Attack, 38 Defense, 87 Agility, and 26 Luck. Their resistances to all four elements remains the same. They also have the same attack options as before, they now each carry a nut. Each Thief yields 115 EXP and 169 coins. They'll also give Felix the Golden Boots as a sort of peace offering.

Bandit
In Golden Sun, Bandit is encountered concurrently as the the two thieves. The Bandit has 244 HP, 46 Attack, 8 Defense, 20 Agility, and 3 Luck. He can attack physically, defend, and use the Monster Skill Slice, for enhanced damage to a single target. He carries a single herb and Smoke Bomb. When defeated, he yields 36 EXP, 46 coins, and drops a Bandit's Sword. Together all three enemies yield 66 EXP and 110 coins. In the rematch against the three in The Lost Age, Bandit has 346 HP, 200 Attack, 41 Defense, 98 Agility, and 34 Luck and now carries two nuts and a single Sleep Bomb and Weasel's Claw. When defeated Bandit yields 136 EXP and 183 coins, for a total of 366 EXP and 521 coins.

Brigand
In battle, Brigands have 421 HP, 251 Attack, 69 Defense, 104 Agility, 5 Luck, and even resistance to all four elements. Their attack options remain the same as the previously fought Bandit.

When defeated, Brigand yields 162 EXP, 190 coins, and sometimes some Crystal Powder. Being sub-boss like enemies, Brigands are stronger than the lesser monsters fought randomly in the fortress' basement, however, they can succumb to the Assassin Blade's Unleash effect.