Ergo Sum received a catalyst shortly after the release of The Final Shape, adding a new gimmick to Destiny 2's first special ammo sword. While Ergo Sum borrows its benefits from other Exotics, the catalyst touches on the weapon's original ability.
Destiny 2: Get the Ergo Sum Exotic Catalyst FAST & EASY! – Grandmaster Excision Guide
Ergo Sum becomes available after completing the Destined Heroes Exotic quest, which awards more Prismatic pieces and wraps up a large portion of The Final Shape's post-campaign missions. This weapon is also known to use special ammo, and players can farm rolls for it in one of the three Overthrow zones in the Pale Heart after completing the quest.
Being farmable is a big help for Ergo Sum. It rolls random frames and Exotic perks from different weapons, so it might take a while before you can get a specific roll. However, if you're lucky, you might also drop an Exotic class item from one of the Pale Heart chests, provided you've completed the Dual Destiny mission.
Here's how to get the Ergo Sum catalyst in Destiny 2, along with a brief explanation of what it does so you can decide if it's worth the challenge.
