Citadel ended September with 91% fewer Palantir shares, despite the stock's eye-popping gains, after selling about 5.2 million in the third quarter. Citadel also hedges its common stock position with lots of put and call contracts. Overall, though, it looks like Griffin isn't expecting the AI giant's bull run to continue.

Warren Buffett and Ken Griffin share a few things in common. Buffett's Berkshire Hathaway portfolio includes only 43 stocks and exchange-traded funds (ETFs). Griffin's Citadel Advisors hedge fund owns positions in over 5,

Billionaire hedge funder Ken Griffin may be tied to a condo takeover attempt in Miami’s Brickell, next to his planned bayfront supertall.

Ken Griffin started the Citadel hedge fund in 1990. In the third quarter, Griffin and Citadel more than tripled its stake in Viking Therapeutics (NASDAQ: VKTX). Wall Street analysts are sticking their necks out and predicting big gains around the corner.

Given Buffett's fairly consistent outperformance of the benchmark S&P 500, both professional and everyday investors wait on pins and needles to see which stocks he's been buying and selling. This can be done with relative ease thanks to the quarterly filing of Form 13F with the Securities and Exchange Commission.