Faceless Runner

Faceless Runners are hostile mobs that spawn in the Underground of the Overworld. It is a melee mob which is very agile, and can fit into 1x1 spaces, it will only spawn below Y = 40.

If the Faceless Runner misses it's charge, it will circle around and charge again.

References/Sources
http://adventofascension.gamepedia.com/Faceless_Runner