Thurindir has a Setup action that lets you search your deck for a Side Quest and add it to your hand.
It looks to me like you draw your initial hand of 6 cards and do your mulligan before doing the "quest setup" steps, but I'm not seeing anything in the Race Across Harad rules that clarifies the timing of Setup triggers on player cards. What do we think? Does Thurindir's ability also happen after the mulligan has taken place?