I made this because of how poorly made my End Barnacle mob skin was.

Runecasters are strange. Their heads hover between four platforms on a plastic shell. Inside the platforms of their plastic shells are magnetic structures that the head uses to stay floating. The chitinous head emits an extremely low-pitch frequency to echolocate and find intruders. When an anomaly or intruder is detected, it raises a purple plasma ring, enabling it to attack. It will then fire a magic missile toward the anomaly. On contact with a surface, the projectile explodes and sends it into the sky; but when two collide, they summon another Runecaster to join the fight. Runecasters are commonly used as sentries to defend Enderian structures. Due to their unique set of traits, Runecasters are considered biomechanical.