Sandalphon is the Eighth Angel, and is discovered by the Mount Asame Earthquake Laboratory inside the volcanic crater of Mount Asame. Unlike the other Angels, Sandalphon does not attack NERV or New Tokyo-3, as it is discovered while still in its embryo state. Believing the capture of a live Angel to prove highly beneficial, NERV Commander Gendo Ikari convinces the Human Instrumentality Committee to go on the offensive.
While Evangelion Unit-02 successfully captures the embryo inside an electro-magnetic cage, it suddenly begins to hatch and mature. It quickly breaks free and proceeds to attack Asuka Langley Sohryu and Evangelion Unit-02.
In its mature state, Sandalphon resembles a fish-like creature, or more accurately an Anomalocaris, the Earth's first carnivorous creature that lived during the Cambrian Period. It is noteworthy that in its embryo state the Angel looks human, and it is not until birth that its physical form alters. Upon birth Sandalphon evolves into a form best suited to survive in its surroundings, in this case the high-temperature, high-pressure conditions of volcanic lava.
The Angel does not appear to have any special attacks or any long-range capabilities. This could conceivably be because it was just born, and has not yet learned such abilities (previous Angels tend to learn such abilities during combat).
Sandalphon's combat abilities are limited to restraining a target with its flexible arms and attacking it with its powerful teeth. Some fans speculate that this may not be a form of attack at all, as the Angel's behavior strongly resembles that of an infant child, possibly looking to its mother for nourishment (nursing).
Regardless, even with its powerful AT Field neutralized by Evangelion Unit-02, Sandalphon's sheer physical durability proves immune even to a direct assault using a Progressive Knife. It is eventually defeated when Evangelion Unit-02 reroutes some of its coolant at the Angel. By using the concept of thermal expansion (stating that objects will expand when heated and contract when cooled), Sandalphon's impenetrable skin tissue sustains heavy damage by the cooling process, leaving it considerably weakened. This in turn allows Asuka's Progressive Knife to penetrate its tough exterior. Once this happens, Sandalphon's body disintegrates under the pressures of the lava.