Alexei Navalny, an opposition leader and critic of Vladimir Putin, passed away in a prison as per the Russian prison authorities.

One of Putin’s most prominent and steadfast opponents, 47-year-old Navalny, was being held in a prison around 40 miles north of the Arctic Circle, where he was given a 19-year term under a “special regime.” He had looked scrawny with his head shaved in a January jail video, according to The Guardian.

The reason of his death was not disclosed by the Kremlin.

He had vanished from a prison in the Vladimir area at the beginning of December. He was serving a 30-year term for charges of extremism and fraud, which he had described as political retaliation for spearheading the 2010s opposition against the Kremlin. He didn’t think he would be freed while Putin was still alive.

Moreover, being a former nationalist politician Navalny investigated Putin’s inner circle, campaigned against election fraud and government corruption, and shared the results in stylish videos that received hundreds of millions of views, all of which contributed to the 2011–12 Russian protests.

His political career peaked in 2013 when he received 27% of the vote in a Moscow mayoral election that not everyone thought was fair or free. He identified a palace on the Black Sea for Putin’s personal use, homes and boats used by former president Dmitry Medvedev, all of which remained a thorn in the side of the Kremlin for years.

After being accused of being poisoned with Novichok by Russia’s FSB security force in 2020, Navalny went into a coma and was flown to Germany for medical attention. 

Then, after making a full recovery, he went back to Russia in January 2021, when he was detained on suspicion of violating his parole and given the first of multiple prison sentences that would ultimately result in more than 30 years in prison.

Putin has begun running for president in order to serve a fifth term. As he changed the term limits provisions in the 2020 constitution, he has the potential to become the longest-serving Russian leader since Joseph Stalin if he decides to run for office again in 2030.