One thing you may notice during your early exploration of Shadow of the Tomb Raider is if you find a Treasure Chest and try to open it, you’ll be met with the disappointment of needing a lockpick to do so. Luckily we’re here to help you find it.
You won’t be able to get it until you reach Paititi. During the Side Quest, Dice With the Dead. The last outcast you’ll come across is a merchant. She carries both the Lockpick and the Ascender! Buy them both if you have the cash to do so, because she moves locations after the mission and can be tough to find without knowing where she is. What? You already finished “Dice with the Dead” and now don’t know where to find her? Here are the locations we’ve found her so far:
After buying the lockpick you’ll be able to go back and open all those precious Treasure Chests.
Source: IGN
GameUP24 