The Serpentwood Bow is one of the Bow-type weapons in Shadow of the Tomb Raider. It can be purchased from the Merchant in Paititi for 4200 Gold Pieces.
An ancient shortbow, crafted from the heartwood of an Ipe tree. Strength: Draw Speed, Hold Time
Shadow of the Tomb Raider, merchant menu
The existence of this bow was first revealed in the Shadow of the Tomb Raider - Welcome to Paititi: Walkthrough Video uploaded on YouTube on 23rd July 2018.