How To Get The Ergo Sum Catalyst In Destiny 2: Grandmaster Excision Guide

To obtain the Ergo Sum Catalyst in Destiny 2, players must successfully complete the 12-player pinnacle activity "Excision" on Grandmaster difficulty. This activity requires the completion of "The Final Shape" campaign and the "Destined Heroes" exotic questline to unlock. Once the Witness is defeated on Grandmaster difficulty, the catalyst is a guaranteed drop from the final reward chest.

The Ergo Sum lightweight special-ammo sword is one of the most versatile and build-defining exotic weapons introduced in the Destiny 2: The Final Shape expansion. Because it rolls with randomized exotic perks and archetype frames, it serves as a cornerstone for Prismatic build crafting. Unlocking its catalyst, which features the unique perk Transcendent Duelist, elevates this weapon by generating heavy ammo and extending your Prismatic Transcendence state. However, securing this catalyst requires conquering one of the most chaotic and high-difficulty encounters in Destiny history: Grandmaster Excision.

Pre-Mission Requirements and Fireteam Preparation

Grandmaster Excision is a 2020 Power Level activity that enforces a strict -20 Power Level deficit. Unlike standard narrative activities, survival requires a highly coordinated fireteam, optimized defensive build-crafting, and structured role distribution. Before launching the activity from the Pale Heart directory, ensure every member of your group meets the entry requirements and has prepared their loadout.

Required Prerequisites and Entry Checklist

• Campaign Completion: You must complete the entire "The Final Shape" campaign on any difficulty.
• Exotic Questline: Complete the "Destined Heroes" exotic quest to obtain your first copy of Ergo Sum.
• Narrative Excision: You must clear the narrative (normal) version of the 12-player Excision mission at least once to unlock the Grandmaster node.
• Power Level Threshold: Reaching a minimum gear score of 2000 (boosted to 2010+ via your Artifact) is highly recommended to mitigate the harsh combatant damage scaling.
• Inventory Space: Ensure your weapon slot and postmaster have free space to avoid post-activity drop glitches.

Recommended Loadout and Team Composition

• Essential Weaponry: At least four players should run Microcosm for rapid Tormentor and Subjugator shredding. Kinetic Tremors weapons, Outbreak Perfected, and high-impact Linear Fusion Rifles are premier choices for safe, long-range damage.
• Utility & Support: At least three Warlocks running Well of Radiance paired with Speaker's Sight for continuous healing turrets, and at least two Titans utilizing Sentinel Shield (Ursa Furiosa) or Ward of Dawn for mobile protection.
• Debuff Specialists: Hunters running Shadowshot (Deadfall) or Nightstalker builds to tether massive waves of Grim, Husks, and Chieftains, controlling the chaotic battlefield.
• Champion Counters: Ensure your fireteam has a balanced distribution of Overload and Unstoppable champion counters. Hand Cannons, Pulse Rifles, and subclass abilities (Stasis Slow, Strand Suspend) are vital.

Step-by-Step Grandmaster Excision Walkthrough

Executing a flawless run of Grandmaster Excision requires splitting your 12-player fireteam's focus between crowd control, plate defense, and elite giant-slaying. Follow these phases to secure your victory.

Step 1: Secure the Initial Landing Zone and Capture the Plates

Upon loading into the Pale Heart's threshold, your primary goal is to charge the Light Wells by capturing three distinct plates scattered across the arena. The enemy density here is extreme, featuring aggressive Dread combatants and high-tier Champions.

1. Split into Three Squads: Divide your 12-player team into three groups of four. Assign one group to the Left Plate, one to the Center, and one to the Right.
2. Deploy Healing and Defensive Rifts immediately: As soon as you reach a plate, Titans must drop barricades and Warlocks must deploy healing rifts. Do not stand in the open; the sniper Dread (Psions and Grim) can easily one-shot players at a -20 Power deficit.
3. Prioritize Overload Champions: Overload Chieftains will rush the plates. Use Overload submachine guns, auto rifles, or Stasis Duskfield grenades to stun them instantly. Focus fire with heavy weapons to melt them before they recover.
4. Coordinate Plate Transitions: If one side captures their plate early, they must not push forward alone. Rotate to assist the remaining plates. Once all three plates are fully charged, the barrier blocking the path to the canyon will dissolve.

Step 2: Push Through the Canyon and Eradicate the Cornerstones

The transition zone is a narrow canyon packed with Unstoppable Ogres, Tormentors, and continuous artillery fire from the Witness. Slow, methodical progression is mandatory.

1. Clear from Distance: Do not rush into the canyon. Use Scout Rifles, Bows, or Sniper Rifles to pick off the snipers on the high cliffs.
2. Stun and Melt Unstoppable Ogres: As you round the first bend, two Unstoppable Ogres will charge. Hit them with Hand Cannon shots or Strand Suspend effects. Once stunned, use Microcosm or Rocket Launchers to eliminate them quickly.
3. Manage Tormentor Aggro: A Tormentor boss will block the path. Use a Titan Ward of Dawn or Sentinel Shield to draw its aggression while the remaining players target its shoulder weak points. Once the shoulders are broken, direct all heavy damage to its chest.
4. Collect Ammo and Orbs: Before jumping into the final portal to the Witness's arena, let your support players generate Orbs of Power using their Supers. Ensure everyone has maximum Special and Heavy ammunition.

Step 3: Survive the Witness Phase and Collect Light Fountains

The final arena is a massive platform facing the colossal form of the Witness. Here, the mechanics require absolute spatial awareness and swift movement.

1. Dodge the Resonance Attacks: The Witness will telegraph attacks by highlighting sections of the floor in orange. Immediately jump or strafe out of these zones. Getting hit by a Resonance blast is an instant death on Grandmaster difficulty.
2. Slay the Bound Subjugators: Two massive Subjugators (Stasis and Strand variants) will protect the Witness. You must defeat them to reveal the Light Fountains. Use your Supers freely here, as killing these targets will drop massive amounts of Orbs.
3. Gather Light to Charge Transcendence: Throughout the arena, glowing fissures of Light will appear. Interacting with these charges your Prismatic Transcendence meter. Every fireteam member must prioritize gathering these to break the Witness's shield.
4. Coordinate the Shield Break: Once your team is fully charged with Light, gather near the center rift. Coordinate your attacks to shatter the Witness's defensive shield, triggering the DPS phase.

Step 4: Maximize Damage and Defeat the Witness

When the Witness is vulnerable, the fireteam must jump onto the central DPS plate. This phase is timed, highly lethal, and demands perfection.

1. Stack Healing and Damage Buffs: Drop a Well of Radiance at the back of the DPS plate. Titans should block incoming collateral damage with Sentinel Shields.
2. Watch the Witness’s Hands: During the DPS phase, the Witness will swipe its hands across the plate or slam them down. Watch the visual cues: if a hand sweeps horizontally, jump over the energy wave. If a hand slams down, run to the opposite side of the plate.
3. Unleash Optimal DPS: Utilize high-tier damage options. Microcosm deals massive bonus damage to the Witness's weak spots. Linear Fusion Rifles and Golden Gun Hunters should target the exposed glowing chest vulnerabilities.
4. Reset Safely: If you do not defeat the Witness in one phase, immediately jump off the plate when the screen begins to turn red. Retreat to the outer platforms, revive fallen teammates, and repeat the Light collection process.

Once the final sliver of the Witness's health is depleted, the mission will end. Navigate to the reward chest at the front of the stage to claim your Ergo Sum Catalyst.

Ergo Sum Catalyst Specifications and Grandmaster Modifiers

The Ergo Sum Catalyst changes the economy of Special Ammo swords by rewarding players who lean into the Prismatic subclass structure. To understand its value and the environment in which you must acquire it, analyze the technical details below.

Common Grandmaster Failures and Fireteam Corrections

Due to the sheer volume of players and enemies in Excision, runs can fall apart rapidly. Recognizing these failure points and knowing how to correct them is the difference between a successful clear and a trip back to orbit.

1. Wiping During the Witness DPS Phase due to Resonance Attacks

• Root Cause: Players tunnel-vision on their damage numbers and fail to notice the Witness raising its hands, leading to multiple simultaneous deaths on the narrow damage platform.
• Actionable Fix: Designate one player as the "Callout Lead." This player’s sole job during DPS is to watch the Witness's physical movements and yell "Jump" for horizontal sweeps or "Left/Right" for vertical slams. The rest of the team must prioritize dodging over squeezing out one extra shot.

2. Running Out of Revive Tokens in Phase 1

• Root Cause: Players spread out too far across the arena, getting picked off by snipers or rushed by Subjugators without support, resulting in rapid token depletion.
• Actionable Fix: Establish a "buddy system." Never defend a plate or chase a Light fissure alone. If a player dies in a highly exposed area, do not attempt an immediate manual revive. Instead, have a Sentinel Titan block with their shield or use a Hunter's invisibility smoke bomb to secure the revive safely.

3. Overwhelming Champion Pressure on the Side Plates

• Root Cause: The left or right plate groups lack the correct elemental counters or weapon types to stun incoming Overload Chieftains, causing them to get pushed off the capture point.
• Actionable Fix: Before starting, verify that every squad of four has at least two direct champion counters. If a plate is being overrun, the center group must deploy a long-range support tool, such as a Bleak Watcher turrets or a Deadfall void tether, to halt enemy progression from a distance.

Frequently Asked Questions

Does Ergo Sum need to be equipped during Grandmaster Excision to get the catalyst?

No, you do not need to have Ergo Sum equipped, nor do you need to have it in your active inventory during the mission. As long as you have unlocked the weapon on your account by completing the "Destined Heroes" quest, the catalyst is a guaranteed drop from the final reward chest upon completing Grandmaster Excision.

Can I obtain the Ergo Sum Catalyst from normal Excision?

No, the catalyst is exclusive to the Grandmaster difficulty of Excision. Completing the normal or narrative versions of the mission will yield standard gear, Pale Heart weapons, and occasional Ergo Sum rolls, but the catalyst will not drop.

What is the fastest way to complete the 500 kills required for the catalyst masterwork?

The most efficient method to complete the catalyst masterwork is to load into the Shuro Chi encounter within the Last Wish raid or enter the opening encounter of the Grasp of Avarice dungeon. Use a Prismatic subclass with high ability regeneration to enter Transcendence frequently, allowing you to defeat large waves of thrall quickly.

Are there checkpoint saves available for Grandmaster Excision?

No, Grandmaster Excision does not feature checkpoint saving. The activity must be completed in a single continuous session from the initial launch to the final boss defeat. If your fireteam returns to orbit or disconnects, you must restart the mission from the very beginning.

Elevate Your Prismatic Build

Unleash the true potential of your exotic arsenal by taking your newly mastered Ergo Sum into the deepest endgame activities Destiny 2 has to offer. Equip your catalyst, rally your clanmates, and dominate the battlefield with infinite Transcendence.