Caroline Ellison is a math whiz, trader, and shadow figure behind FTX's collapse. She's testifying this week in the criminal trial of her ex-colleague and boyfriend, Sam Bankman-Fried.

The late Supreme Court Justice Antonin Scalia reportedly lived in Ellison's former home, she wrote on her now archived Tumblr blog, worldoptimization.

Her father, Glenn Ellison, is the department head of economics at the Massachusetts Institute of Technology and her mother, Sara Fisher Ellison, is a senior lecturer in economics at MIT.

Ellison and her two sisters "definitely got exposed to a lot of economics" growing up, she told Forbes. When Ellison was 8, she gave her father an economics study analyzing stuffed animal prices at Toys 'R' Us for his birthday in lieu of a card, Forbes reported.

And her father supported her interest in the subject, too.

He encouraged her and her siblings to enter math competitions — which Ellison continued throughout middle school and high school, according to the Washington Post.

Ellison said she picked Stanford because she wanted to get away from Boston and "try something different," she said on The FTX Podcast in 2020.

Though she contemplated studying linguistics, political science, or computer science when she was a freshman, she said on the podcast that she opted for mathematics because there were more opportunities to take other classes on the side.

It's a philosophy that examines how people can use their time, money, and resources to best help others. She eventually joined Stanford's Effective Altruism Club and became its vice president, according to Forbes.

In later years, the extent to which Ellison believed in EA has become unclear. She seems to have renamed her Tumblr blog from "worldoptimization" to "Fake Charity Nerd Girl" at one point.

Ellison spent around 18 months as a trader on Jane Street's equities desk and said on the FTX Podcast that she "loved it."

Ellison also met Sam Bankman-Fried at Jane Street, and the two reportedly bonded over their interest in effective altruism, for which SBF became a poster boy.

The switch from Jane Street to Alameda was initially challenge for Ellison, she has said.

"I wanted to be an expert on everything, but there was still lots of stuff in the crypto world that I knew nothing about," she said on The FTX Podcast, adding that she "had to learn a whole new set of intuitions."

Just a couple of weeks after Ellison started, though, Caroline Ellison called her mother, concerned that she'd made the biggest mistake of her life, according to Michael Lewis's biography of Bankman-Fried, "Going Infinite: The Rise and Fall of a New Tycoon," which was released earlier this month.

Ellison and her colleague Sam Trabucco took over from Bankman-Fried as co-CEOs of Alameda in late 2021, and the duo were featured in Forbes' 30 Under 30 list in 2022.

"Though Ellison made some trading decisions, she frequently consulted with Bankman-Fried, particularly about strategic issues and significant trades," the regulator said in an SEC complaint.

All the members were reportedly paired off in relationships with one another at some point. Ellison had an on-and-off relationship with Bankman-Fried and he even made her a list of the pros and cons to dating him, according to Michael Lewis's book about Bankman-Fried.

"In a lot of ways I don't really have a soul," Bankman-Fried once wrote to Ellison, according to Lewis. "There's a pretty decent argument that my empathy is fake, my feelings are fake, my facial reactions are fake. I don't feel happiness. What's the point in dating someone who you physically can't make happy?"

Lerner has likened himself to an "in-resident coach" and worked with the FTX crew for about 32 hours a week while maintaining a small private practice on the side, a Vice report said.

He has also said the collapse of FTX was "devastating" and that its employees felt "like a family."

"Caroline didn't have a lot of gravitas," one former staffer told The Financial Times, who thought she was "an intern" when they first met.

Court documents filed in March show that Ellison received about $6 million as the CEO of Alameda, while her colleagues, including Nishad Singh, FTX's former director of engineering, and Zixiao "Gary" Wang, received hundreds of millions.

Meanwhile, Bankman-Fried himself transferred $2.2 billion into his accounts, per those filings.

However, a lawsuit that FTX subsequently filed in July against its former deputies, including Ellison, shows that she allegedly improperly took $22.5 million in bonus payments from Alameda. She invested millions of that into an AI startup, according to Bloomberg, which noted that OpenAI rival Anthropic is Ellison's only investment on PitchBook.

She left behind a trail of hot takes on crypto, polyamory, and race, apparently posting on X under the handle @carolinecapital, and apparently on two Tumblr accounts, worldoptimization, and worldoptimization-lifeadvice.

On her Tumblr, worldoptimization, she said that crypto was "mostly scams and memes when you get down to it" but she's also seen "a real and pressing need for crypto."

She also compared the polyamory in the Bahamas house to an "imperial Chinese harem," noting on worldoptimization, that there was an established hierarchy and everyone knew where they fell within it.

Ellison said on The FTX Podcast that her parents read the first Harry Potter book aloud to her when she was just 3, and she read the second book by herself at the age of 5.

Her literary tastes, however, range far and wide. Among the last books she reviewed on worldoptimization are "The Golden Enclaves" by Naomi Novik and "Venomous Lumpsucker" by Ned Beuman, and she also appeared to enjoy the work of journalist Matthew Yglesias.

Ellison said that working with Trabucco was "an incredibly formative experience" in a post on X at the time.

Her last post on X was on November 6, 2022, when she came out in defense FTX's balance sheet — in light of the bombshell Coindesk report that set off FTX's implosion.

Bankman-Fried had told Ellison to publicly reassure investors about Alameda's financial stability. In the post she noted that the balance sheet was only for "a subset of our corporate entities" and that "we have > $10 billion of assets" and "hedges" that weren't listed.

Before Ellison struck a plea deal with the Department of Justice to cooperate with authorities, she was facing up to 110 years in prison.

Her entries, first reported by The New York Times, describe a sense of alienation and weariness with Sam Bankman-Fried and his enterprise.

She wrote in 2022 that, "At the end of the day I can't wait to go home and turn off my phone and have a drink and get away from it all," according to the report. She also noted that her romantic history with Bankman-Fried made Alameda "too associated with you in a way that was painful."

Ellison also seemed to doubt about her capacity to lead Alameda, noting that she struggled with "leadership" and "decisiveness" in a document from April 2022, according to the Times. "Running Alameda doesn't feel like something I'm that comparatively advantaged at or well suited to do," she wrote, the Times reported.

The meeting — which took place just days before FTX went bankrupt — was recorded by a former staffer, according to a court filing from August previously reported by Insider.

"Alameda will likely wind down once we can, like, repay all of our creditors and sort of wind down a bunch of our, like, whatever remaining obligations we have," Ellison said in the meeting, according to prosecutors. When an employee asked who decided to use FTX customer deposits, Ellison responded with "Um…Sam, I guess," according to the filing.

In the filing, prosecutors also shared a memo that Ellison wrote, "Things Sam Is Freaking Out About," which they said details her thoughts on the alleged scheme between FTX and Alameda.

They plan to introduce the memo into the trial as evidence that Ellison was acting on Bankman-Fried's behalf, prosecutors said.

Ellison has already figured as a key character in the trial — which began on October 3. During the opening statements of the trial, Bankman-Fried's attorney, Mark Cohen, portrayed Ellison as a "math nerd" who failed to factor in risk management.

He also argued that Bankman-Fried had asked Ellison to hedge Alameda's positions to prevent it from losing money, but Ellison had failed to listen.

Ellison attorney did not respond to Insider's request for a comment.