SFTDP. More details:
It's not like the Quicksilver glitch that can be activated in the Fogstone Depths, where everything moves at half speed. I'm definitely moving twice as fast as normal compared to the movement speed of other characters and enemies.
However, from some experience, it seems others can't see me moving twice as fast, so it's great for speed dodging through a dungeon myself, but not super useful when trying to advance as a group.