Blizzard has released a post stating they are disabling the Unique power of The Umbracrux temporarily in Diablo 4 Season 5 to address an experience gain glitch.
The Umbracrux is a newly added Unique in Season 5 for Rogues, with a very unique ability allowing it to spawn a Shade Totem that redirects damage taken onto enemies surrounding it. While there is no ETA for this fix, Blizzard has stated that the dagger will still be able to drop as loot; it just cannot have its Unique power activated.
