The Great Board is a sub-area of the Field in the Dark World. It is made up of a path composed of black and red squares in a checker pattern, with a width ranging from two to four squares. It consists of several rooms which the party must traverse in order to reach the Forest. Lancer tells the party that the Great Board is the halfway point to Card Castle.
The party first enters the Great Board after leaving the Field. Inside, there are multiple puzzles that the party avoids in order to proceed. Additionally, the Great Board is guarded by a line of Ponmen who leave their pedestals to pursue the party as they walk by.
Eventually the party encounters Lancer again, who, having learned from Susie's advice on how to be scary, confronts the party in a menacing manner along with a bucket to clean up "the mess." Susie compliments Lancer on his improvement, and Lancer tells the party that he'll get them next time, before realizing the party doesn't have a name yet. Lancer suggests that everyone puts a note with their preferred team name into the bucket, so that Kris can randomly choose the party's team name. After Kris chooses a new team name, Lancer takes the bucket and runs off further into the Great Board.
The party proceeds and encounters Mr. Society and Mr. Elegance, before moving on to the final room. There, Lancer awaits the party, warning them of a terrible danger that lies ahead. This danger turns out to be a C. Round, and Susie points out that the C. Round isn't dangerous, nor scary, at all. At that moment, however, the C. Round moves onto the final row of the Great Board, and is crowned into a King Round. The party then engages in combat against the K. Round. During the fight, Susie continues to ignore Kris's commands, and attacks the enemy. This, however, only results in K. Round healing and becoming stronger, reverting Susie's damage and harming the party.
After the party defeats K. Round by knocking its crown off, it transforms back into a C. Round and rolls away. Ralsei then explains to Susie how she hasn't been helping the party, but instead has been acting as an obstacle. He reminds Susie that she is a hero, and asks her to start acting as one. Susie admits that she's been a bad hero, and promises to change her ways, before revealing that this means she'll instead join Lancer to become a bad guy. After Susie and Lancer team up, they continue to exit the Great Board. Ralsei wonders if he's been too hard on Susie, but then acknowledges that she'll probably turn around again, walking with Kris into the Forest.
- The Great Board is used by both checkers and chess pieces, but only white chess pieces and red checkers are seen there.
- Arriving at the farthest row of a checkerboard allows a checker to be "kinged." However, C. Round moved in a straight line to arrive at the edge of the board, a move legal for several pieces in chess but not in checkers.
- Although scattered with both chess pawns and checkers, the red-and-black gameboard in the Unused Classroom, an analogue to the Dark World's Great Board, is identified as a checkerboard.
- The Great Board has an unused theme. Toby Fox explained that he thought giving the area its own music would raise expectations for it too much.
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