Get the bonusmerchants....they´re worth it...
the items they sell are very powerfull:
SPOILER AHEAD
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Robe of Vecna AC 5 Mag. res. 10% casting time down by 4
Plate of Balduran AC-1 +4 hitpoints +1 to charisma
Everhards sling +5 req. no bullets
are some items that I wouldn´t let my party fight without
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