Elden Ring: Shadow of the Erdtree's backhand blades were already a new favorite weapon for me, but the underhand assassin curved swords have an incredible depth of movement tech I wasn't even aware of, like being able to completely no-sell the most devastating boss attack FromSoftware's ever created.
Curiously-named Elden Ring YouTuber Sax Slave Gael explains the blades' anti-Malenia properties in a video overview lauding their moveset. It all comes down to the Swift Slash ash of war, which can only be paired with the base backhand blades or throwable Smithscript Cirque version. Swift Slash is just sick as hell, a chargeable anime dash attack with a slightly delayed blade explosion at the end.
It's already developed a strong following and attending backlash in Elden Ring's PvP, where the ability'sgotten a small, mode-specific nerf—though it still seems like a winner against other players. Swift Slash remains untouched in PvE, where its quick activation, versatility, as well as high damage, stagger, and status build up lend it to taking on Elden Ring's hardest bosses.
Gael demonstrates how it can be used defensively as well: It's possible to just launch it away from Malenia at the beginning of Waterfowl Dance, out-distancing her like you used to be able to with the Bloodhound Step ash of war. More juicy though is juking Malenia by aiming a charged Swift Slash behind her right at the beginning of the attack. "It certainly isn't as easy as it looks here," Gael cautions, but it still strikes me as a safer option than disabling lock-on and running in a circle around Malenia to avoid Waterfowl Dance, or otherwise perfectly timing your blocks with the Sekiro mode Deflecting Hard Tear.
Gael wonders if the ability might get a nerf down the line, but I hope not: Shadow of the Erdtree's extreme challenge demands tools that are up to the task, and I want to go ninja dashing all the way through New Game Plus at some point in the near future.
If you want to grab Swift Slash for yourself, you'll want to follow Hornsent's Quest in the DLC and side with him when conflict arises with another character. As for the backhand blades themselves, you can find them right at the beginning of the DLC in the northeast of the Gravesite Plain. Bleed or Frost infusion seem like the way to go, and Swift Slash benefits greatly from both the Shard of Alexander and Godfrey Icon talismans.