- Comments made by the mother of Toom's best friend during her childhood.(src)
Toom grew up as the daughter of the vice president of the Kal-Bryant Mining Conglomerate on Pridewater and was often present when he conversed with board members via hologram. Her psionic powers manifested at a young age, with her being able to sense her father's thoughts and feelings and excel at games that involved intuition with other board members' children. Her father was concerned, telling her that her knowledge wasn't natural and she would have to see a doctor. The other children began to ostracize her also, not wanting her to play games with them because she always won.
Under the Terran Dominion, Toom became a student at the Ghost Academy. She joined Team Blue as a third-class ghost trainee. Gabriel Tosh, the team's leader, welcomed her, and a spark was established between the two from the start. However, Toom tried to ignore it.
In an early training simulation, the understrength team attempted to rescue hostages from the Valerian. Tosh gave instructions, but Nova Terra promptly ran off to carry out the mission on her own. Toom sneaked into the planet-hopper but didn't check for booby traps, leading to her "death" and a low rating. Terra was the only student who came close to completing the mission, and despite her lack of teamwork she received a high rating from "Sparky" and Preceptor Lagdamen. Toom complained about Terra's lack of teamwork, but Lagdamen believed bad teamwork was worse than no teamwork.
Toom was upset about this, and when another ghost trainee, Dylanna Okyl, rudely confronted Terra on this, Toom wanted to make her thoughts known. Tosh, however, preferred to handle the situation privately. When he tried to get her to improve her teamwork, Terra brushed him off and left, prompting Toom to call both Terra and Okyl "slikes". Toom also told Tosh she thought Terra was getting preferential treatment due to her high PI score 
Making Friends and Enemies
Sorry, but there's no excuse for you, Mr. son-of-the-finance-minister."
- Toom and Cistler's emnity begins.(src)
Kath Toom was approached by new teammate Aal Cistler, who immediately began hitting on her. Cistler was the son of Terran Dominion Treasury Ministry head Aldeo Cistler, but as the daughter of a vice president of the Kal-Bryant Mining Conglomerate, she wasn't impressed by him. She then stated the various reasons she was unimpressed, including having met more interesting men previously. She said that while at the Conglomerate, she and Travski, whose uncle was a computer tech there, would have nothing to do with each other, at the Academy, they were all equal. She predicted Aal Cistler would soon wash out. Cistler, plotting revenge, arranged for Toom's father to be put under investigation for "accounting irregularities" involving Sector 9.
Nova Terra's attitude improved to the point where she would help Toom on training assignments, prompting Toom to ask what happened to the old Nova Terra. The two bonded over their similar backgrounds. However, Toom received bad news from her father, currently under investigation by the treasury ministry due to Cistler's scheming. At the time, she didn't think too much of it...
Later, Team Blue successfully carried out the Valerian training mission again, with Toom receiving a 70% rating, and Aal Cistler was thrown out for dealing drugs (but not punished due to his father's influence). However, Toom swiftly received bad news; not only was her father unable to contact her due to Cistler's machinations, but he sent her a mocking message letting her know he had been behind it.
Red vs. Blue
I will never be your sweetheart!"
- Cistler and Toom at the start of their sparring match(src)
Even with Cistler gone, there was enough enmity in the Ghost Academy to go around, with Team Red providing it. An exercise against zerg-bots was a case in point, Toom backing Terra up when she and Okyl came to verbal blows. It was team antagonism that wasn't helped when Cistler returned to the academy, this time becoming part of Team Red. He challenged Toom to a sparring match during training under Sergeant Hartley and taunted her with the knowledge her father had been imprisoned, allowing Cistler to defeat her when she became enraged and lost her concentration. Still, there was at least some good news when fellow team member Lio Travski returned from detox, Toom being glad to see him again. However, while he told her not to let Cistler get under her skin, she was wary as to whether he would be up to the upcoming training simulation against Team Red, given his poor record. To make matters worse, Terra and Tosh had begun a relationship, though she let it run its course.
No problem! Let's see how they do against explosive rounds."
- Lagdamen and Toom during the battle(src)
Upon the anniversary of the Fall of Tarsonis, Teams Red and Blue were combined into Team Purple under the leadership of Gabriel Tosh. Toom and Cistler could not get along, since Cistler constantly taunted her about her father. Tosh told her they had to work together and not fight over that.
The team was sent on a training mission to The Baker's Dozen on the battlecruiser Cyrus—originally to the fifth planet, but the fourth world of the star system became the training ground upon detection of a distress signal sent by Old Family heirs under siege by the zerg. During the mission, Toom proved to be a good shot with her C-10 rifle, downing numerous zerg. However, while they were able to secure the survivours, the Cyrus was downed, stranding them on a planet teeming with zerg. Toom suggested that Terra and Tosh could take on the main hatchery, drawing the zerg away from the battlecruiser, only for Nova to eliminate the xenomorphs with a psionic blast. The plan was followed through, with Toom and the others heading for the Cyrus. Toom used her rifle to take out approaching overlords, downing them all with single shots to their vital organs.
The plan worked and the team made it back to the Ghost Academy the survivors, but Emperor Arcturus Mengsk ordered them memory wiped. Toom was left with the belief that the mission had been canceled and was upset she didn't get to use her rifle.
Love and Loss
Sometime after the events on Shi, Tosh and Toom started a romantic relationship, one that became quite physical. The pair discovered that Toom's father had committed suicide in light of the investigation into the Kal-Bryant Mining Conglomerate. However, Toom's memory of these events was wiped. To make matters worse, Tosh was apparently killed on one of his first missions away from the academy. Toom and her friends believed him to be dead.
Eventually, Toom became a fully fledged ghost. As was standard procedure, she received a full mind wipe, forgetting her past life, and received the designation of Agent X52735N. Toom took part in an operation on the planet Gohbus to pursue a band of pirates.
- Tosh addresses Toom(src)
In 2503, Toom was dispatched to the lawless world of Altara charged with investigating rumors of a UED terrorist cell. There, she was ambushed and captured by Dylanna Okyl. Waking up, she found herself a prisoner of Gabriel Tosh, albeit one that was being treated well. Her neural implant had been removed, her memory was returning to her and her psionic powers had been amplified, thanks to exposure to terrazine. He made it clear that he intended to set her 'free,' and maintained that he regretted the harsh methods he'd used to bring her to his presence.
Over the next few days, Toom became acquainted with the station, as best as someone in her situation could. For better or worse, her exposure to terrazine was rejuvenating her memory, though included hallucinations and vivid dreams. Before long, she began to crave it. During this period, Tosh visited her again, launching into a fiery tirade about freedom and whatnot before inviting her to go on a certain mission. Toom declined however, but still found herself appreciating his fervor and conviction. Indeed, she began to wonder about being set free, and whether Mengsk really was the power hungry dictator Tosh made him out to be, whether the Dominion really was no better than the old Confederacy.
Wandering through the station, she came across a holographic representation of Lio Travski. Thought to have perished in an incident involving Sparky back at the academy, he was in actual fact an AI allied with Tosh. He filled her in on the Ghost Academy's less savoury practices and his belief that he essentially represented the next step in human evolution. Toom terminated the conversation through what she discovered was telekinesis, an ability given to her through terrazine exposure. Such an ability didn't give her solitude from Travski however, who continued to track her movements throughout the station. Toom ended up finding her way to an empty hanger, where she was confronted by a hologram of her father. It was a message from him that explained what Toom had once known prior to her mind-wipe, that the Cistlers had framed him in regards to the Kal-Bryant investigation. More memories came back to Toom and Travski claimed that he had files that proved her father's innocence. He also revealed that her father had tried to get her out of the program, an effort that she'd been kept in the dark about. Toom lashed out, silencing Travski again, but found herself warming to the idea of being a spectre.
Toom was witness to Tosh's gradually decaying mental state aboard the station, as he talked to her about Grandma Tosh appearing to him. Nonetheless, the romantic feelings the two had for one another began to reignite. Later Toom was present to an argument between Tosh and General Cole Bennett, leader of the Project Shadowblade. Tosh began to lash out with his psionic powers, but Toom steps between them, facing the full blast of Tosh's psionic strength. She was blasted back, and ran away. Tosh attempted to follow, but Bennett stopped her.
As she ran away, she found her way to Nova, who had been captured and brought aboard the station. Nova tried to talk her down, but Toom was insistent on stopping her. Nova incapacitated her with a psionic blast, but could not bring herself to kill her old friend. Instead she knocked Toom unconscious and swapped her hospital robe's with Toom's spectre gear. She then fled, using her unconscious form as a distraction.
Bennett and Dylanna Okyl, who had also been indoctrinated into a spectre, found her knocked out in hospital robes. Toom told Bennett Nova had beaten her, and which way she went. Bennett stated that he no longer had any use for her, and psionically attacked the weakened Toom. Toom tried to resist, but slowly was psionically crushed by Bennett, and killed.
Tosh was aggrieved by the death of Toom, and when Oykl informed him he psionically lashed out, killing her. Tosh convinced himself that Toom was still alive, and took her body to the Palatine. After the death of Bennett and the destruction of Gehenna Station, Tosh took her corpse with him with him to Haji, with the intent to restart the spectre program when the time was right.
Personality and Traits
Toom has been described as "mouthy" and "bright, tough, hot" and says things like they are, which was not necessarily a good thing at the Ghost Academy. As a member of Team Blue, she was a team player. As a ghost, Toom resented revealing any weaknesses in her emotional armor.
Toom's talents include skill with a C-10 rifle. Her psionic abilities include telepathy and as a ghost, she had a Psi Index rating of 6.5, though this increased after she underwent spectre enhancement, rising to at least 8. Her psionic powers include telepathy, empathy and after terrazine exposure, telekinesis.