An Immortal is a protoss anti-armor unit with extremely high resilience.
The immortal's in-game strength against armored units and buildings is extremely exaggerated in StarCrafts, with immortals instantly destroying even the most resilient structures and large units in a single blast, as evidenced in episodes such as Onslaught and Three For All. However, their weakness to smaller units is also blown out of proportion, as they are repeatedly defeated by light infantry such as Bob the Ragelot (zealots), zerglings, marines, and even SCVs.
Immortals are yellow quadrupedal robots with twin phase disruptor cannons. Unlike the straight and angular appearance of actual immortal cannons, immortals in StarCrafts have rounded cannons. They have team-colored sections on their cannons and around the cockpit.