Bort is a Gem from the Land of the Lustrous who serves as the community's ultimate combat asset, primarily tasked with frontline defense and patrol duties. Classified as a diamond-grade Gem with a hardness level of ten, Bort possesses both the highest possible hardness and exceptional toughness, making them one of the most durable and physically powerful characters. Their crystalline body structure incorporates small crystallizations that effectively absorb impacts, preventing damage from spreading in a way that distinguishes their composition from a conventional single-crystal diamond.

Personality-wise, Bort is defined by an intense and near-exclusive focus on battle. Other Gems refer to Bort as a battle enthusiast, as they demonstrate little to no interest in activities outside of combat. This preoccupation manifests in a personality that is ruthlessly logical, uncompromisingly strict, and sharply perceptive. Bort communicates with blunt, cutting precision and does not hesitate to point out the weaknesses or shortcomings of their comrades. While this forthrightness can make Bort appear cold, intimidating, or even aggressive, it is rooted in an unwavering commitment to efficiency and protection. Their analytical nature extends to self-assessment as well; during a confrontation with a powerful Lunarian beast, Bort quickly determined that victory was impossible and chose a pragmatic retreat to preserve their strength and warn others, demonstrating that their courage is not reckless but governed by strategic calculation.

Despite this formidable exterior, Bort is not devoid of emotion or vulnerability. Beneath their stoic and harsh demeanor lies a deep-seated protective instinct for their fellow Gems. This is most evident in their relationship with Diamond, their partner. While Bort's habit of criticizing weaknesses drove a wedge between them, causing Diamond to feel inadequate, Bort harbors profound loyalty towards them. When Diamond was shattered and defenseless during an attack, the usually pragmatic Bort abandoned all strategic hesitation and stood ready to fight to the death, no longer acting for the collective good but for the sake of their most precious friend. Similarly, Bort exhibits a softer, more vulnerable side in rare moments, such as an inability to attack the fluffy, dog-like Shiro Puppies, revealing an "adorability" beneath the tough surface.

Throughout the story, Bort serves as a benchmark for strength and a foil to less capable Gems like Phosphophyllite. Initially showing hostility or dismissiveness towards Phos, Bort later develops an interest in Phos's newly acquired gold alloy arms, even going so far as to test their properties with a slash. This curiosity leads to an offer to team up, suggesting that while Bort struggles to relate to others except through the lens of combat, they do care about the development of their allies. Bort’s development is subtle but significant, moving from a pure instrument of utilitarian value to a character whose actions are influenced by personal attachment. At one point, when facing an enemy they could not damage, Bort took command of the situation by grabbing Phos and throwing them to safety, instructing them to ring the alarm bell six times, solidifying their role as a dependable leader who acts decisively under pressure.

In terms of abilities, Bort is unparalleled in raw combat strength. Their hardness and toughness are of the highest quality, allowing them to engage Lunarians directly with minimal risk of shattering. They are an efficient and analytical fighter who uses their strength to serve as a model and guide for other Gems. Their presence on the battlefield is so reassuring that when Bort confronts the Lunarians, the other Gems feel an immediate sense of relief. Their unique body structure grants them superior durability, making them a relentless protector whose harsh exterior is ultimately dedicated to keeping every Gem safe.