Savek is a boss enemy that you can fight during a Wrathborn hunt in Season of the Hunt. You will need a fully charged Crypolith Lure that you can get from The Crow on the Tangled Shore. You will first need to charge your lure by playing Crucible, Strikes, or Gambit, then right-click on the Crypolith lure in your Quests tab.
Place the Savek Prey Mod in the Prey Mod slot, and then place whatever additional mods you have access to and want to use in the other slots. If you have none, just place empty mods in there.
Now, check your map on the Tangled Shore and you will see a new icon of the location of a Crypolith that will start the Hunt. Go there and walk up to the Cryptolith and activate the Lure.
A Fallen Servitor will appear, and when you lower his health enough his will escape. There will be a small Hive ball of energy left behind, and you can interact with it to track him. Follow the trail of green energy on the ground to another podium, potentially in a different region, and interact with it again to be whisked off to the boss fight.
Savek is a simple enough fight, although he is quite strong. The giant Hive is accompanied by some small servitors who keep him shielded. Take them out and they will leave a pool of green energy on the ground. Stand in it for a brief period of time and you will gain the ability to damage Savek. After that, just lay into him with your weapons and rinse and repeat until he is dead. When he dies, he will drop the Deafening Whisper Energy Grenade Launcher.
When it is over, return to the Crow on the Tangled Shore.