My favorite Artifact in Voidwrought is "The Assassin" Soul. It gives the Dash ability invincibility frames where it normally lacks them, making the dash into a much more effective evasive ability than usual, with only a small cooldown between dashes.
Being able to dash through enemies, bosses, and traps creates many more openings to deal damage and quickens the pace of combat. This made some bosses a breeze due to being able to much more easily avoid some of their most powerful attacks, though it isn't a one-size-fits-all answer.
This is such a significant ability that I haven't unequipped it since I obtained it.
An honorable mention goes to the Crystalline Lens, since it gives me access to a burn status effect that allows me to apply damage over time to even large groups of enemies.
