The Battlefield is a giant chessboard-like planet located in the center of Skaia. It is the location at which the battle between forces of light and darkness takes place, and ultimately at the end of Sburb where the heroes must do battle with the Black King.
Each time a Sburb player initially prototypes a Kernelsprite, the size of the board seems to grow exponentially: Where The Battlefield is initially a three by three chessboard (a situation which leaves the only two combatants, the White King and Black King, in an eternal stalemate), the board grows into a full game of chess after a first player's prototyping, albeit with a twelve by twelve square board and some pieces taking up multiple squares.
When a second player prototypes their Kernelsprite, the board expands to a massive cube with forty-eight squares to an edge and landmarks like trees and lakes. The Battlefield becomes a fully spherical planet upon a third protoyping. After the fourth prototyping, The Battlefield appears to have gained a large outer shell made of checkered tendrils.
A 12x-prototyped Battlefield is shown near the end of Homestuck: Act 5 Act 1, but the full planet is never shown.
The final form of the Battlefield is required to create and grow the new universe, fulfilling the objective of the game. This is why a pre-entry prototyping is necessary for each player. According to Rose, the prototypings enable Skaia to transform and heal itself, thus letting it "handle" the aforementioned new universe.
When the Black Kingdom inevitably wins the battle, the Black King uses the White King's scepter to initiate The Reckoning, sending all the meteors in The Veil towards the Battlefield to destroy it. Skaia defends the Battlefield by opening defense portals to stop the meteors, instead sacrificing the session's planet of origin to protect itself. The players' goal is to stop the Reckoning before this happens by defeating the Black King, thereby winning the game. The players then disperse their planets' grist hoards into the Battlefield, preparing it for the Ultimate Alchemy, while one of the players lights the forge.
The trolls' Sgrub session was fairly regular, although they faced a 12x prototyped Black King able to release the Vast Glub, making it an unusually difficult final boss.
Despite being prototyped 12 times, the trolls' Battlefield does not seem to differ from the kids', save for the lily-pad like structures. It should be noted that only the first 3 prototypings seemed to affect the battlefield itself in the kid's session, while the 4th added an additional structure surrounding it. However, it is likely that the troll's battlefield is more complex than an initial view suggests - a book in a Prospit library in the Beta Kids' session talks about further non-euclidean modifications based on the addition of additional orbs to the Queen's ring - a notion that the book's author finds ridiculous because it only has 4 orbs.
It is implied that, upon winning the game, the trolls' Battlefield underwent a transformation. From the, it seems brighter than usual. It possesses a shimmering surface that resembles a spherical pond more than a sky, and multi colored glowing Lilypads are found on its surface.
Of course, this was all interrupted by Jack Noir, who destroyed Skaia and the Genesis Frog within it.
After war begins on The Battlefield, the Warweary Villein, a Dersite farmer who resides on the Battlefield, grows tired of the war and unites soldiers from both kingdoms to rise up against the Black King. Jack Noir murders the Black Queen, obtains the White King's scepter, and starts The Reckoning well before it is intended to begin.
He uses the powers gained by the Queen's Ring to ravage the Battlefield and murder all of the Black and White soldiers, excluding the Warweary Villein. He then severs the massive chain connecting Prospit to its moon, sending the moon crashing down to the Battlefield and killing Dream Jade in the resulting explosion. The Battlefield is left in ruins and with a massive crater.
John's dream self wakes up on The Battlefield, retrieves the White Queen's ring from Dream Jade's body, and sees his immediate future in the clouds. He is assaulted by Jack Noir, who seeks the Ring, but the Uber Bunny comes to his protection.
Rose mentions that the "treasure" known as the Tumor, located in the center of the Battlefield, is critical to her plans; it is later revealed that she plans to destroy the Green Sun with it, taking the power from Bec Noir and all of the first guardians. She also mentions that John must retrieve this object using The Windy Thing.
In Cascade, Jadesprite merged with Jade and rescued the Battlefield from a large meteor using her space powers. Jade then shrunk the inner portion of the Battlefield and took it with her to escape the scratch, leaving behind the "shell".
Jade eventually places this Battlefield into the post-scratch Skaia, allowing the Ultimate Alchemy to take place.
The chessboard that the Wayward Vagabond creates in Can Town in the Skyship Base is a symbolic representation of the Battlefield. In his , the Black side wins, much as Derse defeats Prospit on the Battlefield.
Courtyard Droll blew up the Battlefield, making it all the more necessary for another Battlefield to be deposited.