The Pallas Siegebreaker is a desired reward that you can collect from Spider on the Tangled Shore. He is one of the enemies who escaped from the Prisoner of Elders, and it is up to you to track him down, locate him, and end his newfound freedom. The only clue you are given on the Bounty when you pick it up from Spider is that it can be found on the Tangled Shore.
Finding Pallas’s Siegebreaker is surprisingly easy, and chances are you’ve met him before, and just didn’t realize it. The Pallas Siegebreaker can actually be found at the Public Event that occurs very close to the Spider’s lair on Tangle Shore.
The Cryopod public event involves taking on a couple of waves of enemies, and then a big boss will pop out of the Cryopod and you will have to defeat them. In Tangled Shore, that boss is the Pallas Siegebreaker.
To complete the bounty, the event does not need to be Heroic and can kill the Siegebreaker. However, this event is tied to a couple different missions, so if there are other Guardians there, it is considered polite to ask in the local chant if anyone needs to do the Heroic event before melting the boss down.
If someone needs to make it heroic, just take a third of Siegebreaker’s health, then shoot the leaky vents in the cryopod’s side to expose some orbs. Throw them into the Siegebreaker, then repeat the process one more time to freeze it in place.
After that, you need to defend the area from some waves of enemies and the Siegebreaker will be transported back to the prison. You can then deliver the reward from the Missions tab in the Director.