Casting Speak with the Dead on Baretha - Baldur's Gate 3

The Githyanki fight in Early Access is one of (if not the hardest) fights in Baldur's Gate 3 Early Access. If you win you can cast Speak with the Dead on Baretha, the leader of this particular raiding parties who is scouring the area looking for the artifact that you or Shadowheart have in your possession.