The Blue Lion is the right leg of Voltron and the second massive lion present, being anywhere from ~70 to 100 ft. in length (depending upon the animation frames used to depict it). It is mostly covered in blue save for its limbs and mouth. It has yellow eyes and white ears. Its torso is black with blue exposed at the edges, making it look like fabric. Behind its shoulders is a red section which raises to become a missile launcher and sports the number 4. It has wheel-like bolts in its shoulder and limb joints in order to allow fluid execution of movement. It also has three claws and a white-colored tail.
The Blue Lion resides in waters underneath The Castle of Lions and is therefore Arus' second line of defense. It comes to life once its activation key is placed.
The Blue Lion forms the right leg of Voltron. During formation, it loses its limbs and tail. The Blue Lion affixes to the Black Lion's right leg, the Yellow Lion affixes to its left leg, and the Red and Green Lions affix to its right and left shoulder. The Black Lion's mouth opens up to reveal a humanoid face and its ears open up to form horns and Voltron's transformation is complete.
The Blue Lion has a number of abilities displayed in the show.
- Sentience: The Blue Lion emits some limited sentience without a pilot.
- Flight: The Blue Lion is capable of flying in the air.
- Hovering: It likewise is capable of hovering in a single spot in the air.
- Interstellar Travel: During its voyages outside Planet Arus, the Blue Lion is covered in a blue comet-like aura which it uses to travel from Arus to other planets in the galaxy. This ability is not used within the atmosphere of Arus or any other planets but only in outer space, suggesting it is for interplanetary and interstellar travel.
- Blockbuster Turrets: The Blue Lion uses a triple-barrel weapon materialized from energy in its shoulder bolt. It has vertically placed turrets for firepower. It can manifest on both shoulders or extend from the center of its back. Any of these turrets can fire any of the missile ordnance from the shoulder-mounted cannon.
- Laser Darts: Swift-flying projectiles, each powerful enough to destroy a Doom Blaster with a single hit.
- Shoulder-Mounted Cannon: A powerful cannon weapon shared by the other lions.
- Cryogenic Missiles: Rockets at least three meters in length with a vaguely pis-cine detail. These rockets release a freezing nitrogenous compound upon contact.
- Sword Attack: Contrary to its name, a dagger like a crucifix is materialized from its mouth in order to pierce and cut objects.
- Lion Missiles: It can fire various other miniature missiles.
- Blue Claw Missiles: It can fire off missiles from its claws which have a limited homing capability.