Ancient Phalanx

The Ancient Phalanx is an enemy that is found in Marble Caves, along with Ancient Archers and Ancient Chargers, after Skeletron has been defeated. It walks towards its target to deal contact damage, and periodically raises its shield, granting it temporary invincibility.

Trivia

 * In ancient war times, a phalanx actually refers to a line of hoplites multiple lines deep. This strategy of pushing the front lines was effective in driving back enemy forces.
 * It can be considered the marble equivalent to the Granite Golem.