Kraken is a Ukrainian special volunteer unit formed the same day as the Russian invasion. They have some sort of relationship with Azov and because they were formed from and recruit from the Ukrainian right wing, they are accused by the Russians as being "nazis". (Biden would probably agree.) Formally independent of the Armed Forces of Ukraine (though they coordinate closely), today they operate as the Special Forces (Spetsnaz) arm of the HUR (Main Directorate of Intelligence), so they are something analogous to a more impromptu CIA Special Operations. After Azov lost half its fighters in Azovstal in Mariupol, Kraken has taken their place and have thus ascended to almost mythical status in the Ukrainian imagination.
And Kraken are known for making extraordinary videos of their operations which help to maintain their mystique.
Here's another of their videos, documenting them clearing the Kharkiv oblast town of Kupiansk on the Oskil river, during the recent rout of Russian forces in that area. The video is 30 minutes long, but it's well worth watching all the way through, since it gives a real feeling for what the war is like on the ground.
And warning: this video can be pretty brutal in spots, you see men dying and being shot at close range.
https://www.youtube-nocookie.com/embed/jVvgnHxJoSY