The Destiny 2 The Final Shape expansion has been a bit of a power trip so far. Whether we're talking about the exotic sniper rifle, Still Hunt, which can fire the golden gun super shots when powered up, or the strength of the new prismatic subclass in general. For example, warlocks have been using Getaway Artist to summon both arc souls and stasis turrets at the same time—just one of the many absurd class interactions that players are currently uncovering.

One powerful new exotic that was flying under the radar until recently was the Ergo Sum sword. This energy slot blade—that's right, you can use two swords at once now—is the first of its kind, and is geared specifically towards building both light and dark energy for the prismatic subclass and prolonging that state when [[link]] you use it to get kills. The coolest thing about Ergo Sum is that it's a randomly rolled weapon that picks its trait from a variety of exotics. These include:

• Wolfpack Rounds (Gjallarhorn): Powered heavy attacks cause nearby Sword-wielders to emit tracking missiles with every attack.
• Gathering Light (Traveler's Chosen): Final blows with this weapon grant stacks of Gathering Light, improving guard stats and lunge range. Stowing this weapon consumes all stacks, granting melee, grenade, and class ability energy.
• Sacred Flame (Ticuu's Divination): Powered heavy attacks mark nearby targets, causing them to explode upon death. Striking marked targets with a Light attack detonates them.
• The Perfect Fifth (Polaris Lance): Every five hits attach a delayed Solar explosive, scorching your target.
• Arc Conductor (Riskrunner): Powered heavy attacks charge the wielder, enabling them to resist Arc damage and chain lightning to nearby targets.
• Stormbringer [[link]] (Cloudstrike): Rapid final blows create a lightning storm at the target's location.
• Unplanned Reprieve (Original trait): Powered heavy attacks emit projectiles that detonate with a delayed Void blast.
• Insectoid Robot Grenades (The Colony): Defeated targets drop insectoid robots that chase and explode close to other targets.

As you'd expect, some of these make Ergo Sum really strong, especially when you consider that the weapon also randomly rolls the frame of sword that you get, including the new wave frame sword archetype introduced in this expansion. The strongest perk is probably Wolfpack Rounds; once you perform a heavy attack with the sword, every swing will cause a rocket to split off and track to a nearby enemy, while heavy attacks will create lots of rockets at once. 

Just like firing Gjallarhorn, nearby sword-users will also start creating rockets every time they swing. Imagine the chaos of stacking that on six sword-users in a raid. Since Ergo Sum only takes an energy slot, Wolfpack Rounds will also infuse into any heavy sword you're carrying, so you could do a heavy attack with Ergo Sum, switch to a Falling Guillotine, and suddenly when you do a vortex attack, rockets fire off in all directions. The real question is whether Wolfpack Rounds infuse other player's exotic swords like Lament, because that would be real strong, too.

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So yeah, it's a pretty good sword and you probably want to know how to get it. Thankfully it's quite a straightforward exotic quest, but you will have to unlock it first. Here's what you need to do in order:

• Finish The Final Shape campaign
• Complete the Queens I mission
• Finish the Lost in the Light and Found in the Dark quests. These consist of a couple of missions each helping out Mithrax and Caiatl
• Use the Dyadic Prism that ghost gives you to access the new landing zone and grab Ergo Sum

Excluding the campaign, it's about five [[link]] missions in total, but the Lost in the Light and Found in the Dark quests also unlock the remaining prismatic aspects, grenades, and supers for the class, so they're worth doing anyway. The good news is that once you've got your sword, completing the Overthrow event has a chance to drop more rolls of Ergo Sum. You can also earn extra copies of Ergo Sum through the Pathfinder feature in the Pale Heart—finish any of the paths by completing the individual objectives and you'll be able to claim another copy of the sword. 

I've been messing around with a few different rolls, including Wolfpack Rounds, and having an energy sword with such a powerful trait does go a long way to making them feel even more viable. Now just to find one that spawns insect grenades.