An end game Dungeon in Lost Ark is Phantom Palace and it will become unlocked in one of the Rohendel Region questlines after completing 'A New Voyage' and 'Wall of Procyon' quests from Ealyn the Queen of North Vern in Vern Castle. Inside the Phantom Palace you will find a huge chessboard puzzle which you need to solve before you can fight the boss and complete the Dungeon. This How to Solve the Phantom Palace Chess Puzzle will give you the solution.
You will be told by the in-game quest guide that you need to place the chess pieces 'symmetrically'. In order to do this you need to look at the chessboard and see how the chess pieces are arranged and see it there are any that are missing, black or white. If there are you simply need to pick them up from the side and place them on the chessboard.
The easiest way to solve the Phantom Palace chessboard puzzle is by hovering your mouse over all the chess pieces until a chess piece becomes highlighted in yellow to indicate that you need to move it onto the chessboard. Although the in-game quest guide instructed you to make the chessboard symmetrical you will find that to solve the puzzle you need to mirror the chess pieces' locations or make half the board as if it's rotated 180 degrees.
In the first chess puzzle, the white queen is missing you need to pick it up and place it exactly the opposite of where the black queen is placed.
On the second chess puzzle, you need to pick up the white horse and place it on the opposite side of the black horse diagonal to the white pawn.
On the third puzzle, you need to pick up the black pawn and place it diagonal to the white pawn in the middle of the board and the king.
Take a look at Una's Task Guide to find out how you can earn huge amounts of Gold in the endgame of Lost Ark.
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