What to know

  • Location basics: The Second Sentinel starts dormant in Cogwork Core's west side, behind a breakable wall, and relocates to High Halls for its boss encounter.
  • Requirements overview: Collect three Cogheart Pieces to revive it as an ally; start the Final Audience wish quest for the fight, plus Clawline ability for access.
  • Fight highlights: Expect whirlwind slashes, scissor projectiles, and an X-shaped charge in phase one, ramping up speed in phase two.
  • Rewards and achievements: Earn the Reserve Bind for bench heals, plus "Eternal Devotion" achievement upon victory.

The Second Sentinel is one of the more unique encounters in Hollow Knight: Silksong, blending puzzle-like exploration with quest-based conditions. Unlike many bosses that you stumble across directly, this guardian demands preparation, collection, and a triggered quest before it comes alive as a full fight.

Second Sentinel: Location and requirements

The Second Sentinel is found in the Cogwork Core, part of the Great Citadel. The path is hidden behind a breakable wall, making it easy to miss if you aren’t paying attention to the environment.

To activate it, you must collect three Cogheart Pieces scattered across Pharloom. Once all three are obtained, they combine into a Mechanical Heart, which you insert into the statue of the Sentinel. This act brings the construct to life, allowing it to move around the area, even outside of its boss fight.

Second Sentinel: Unlocking the fight

The Sentinel does not become a boss encounter immediately upon activation. To challenge it, you need to take on the Final Audience wish, a quest that can be accepted from a Wishwall in Songclave.

After accepting this wish, return to the Cogwork Core. This time, the Sentinel will engage you as a full boss fight rather than remaining a passive guardian.

The fight with Second Sentinel explained

Once the conditions are met, the Second Sentinel’s boss battle begins. While exact health and attack values remain less documented than other bosses, several key aspects are clear:

  • Attack style: It relies on mechanical precision, sweeping scissor-like strikes, and heavy forward assaults.
  • Stagger: Roughly eleven clean hits are needed to stagger it temporarily, opening a window for counterattacks.
  • Arena: The fight takes place in a confined mechanical chamber, emphasizing positioning and evasion.

The design rewards patience and careful observation. Dodging through sweeping attacks and punishing its stagger phase are essential for success.

Second Sentinel rewards

Silksong's 52 achievements reward its multifaceted role. Here's a quick list of those unlocked via this guardian:

  • Eternal Devotion (Secret): Defeat the Second Sentinel in High Halls—unlocks after the final blow, with flavor text on its "eternal duty."
  • Heart of the Machine: Collect and insert all three Cogheart Pieces—pops on revival.
  • Audience Granted: Complete the Final Audience wish, including both Citadel sightings.
  • Allied Automaton: Witness the Sentinel aid you in three random combats post-revival.
  • Pharloom's Echo: Use Needolin to play the devotion melody during the quest—ties into broader lore achievements.

How defeating the Second Sentinel helps

This encounter is more than a test of combat skill. It showcases Silksong’s layering of exploration, collection, and quest fulfillment. By requiring Cogheart Pieces and a specific quest trigger, the Second Sentinel demonstrates how Pharloom’s guardians are tightly interwoven with both story and gameplay progression. For completionists and lore seekers, this fight is a mandatory stop on the path through the Citadel.