Sepron is a giant sea serpent and is the second beast to appear in Beast Quest. Before the first book, Sepron is attacked by Malvel the dark wizard and is forced to cause an extreme level of damage to Avantia, instead of protecting it.

Sepron lives in western Avantian ocean, and therefore the damage or protection he causes is there. His main task is to protect the fish and to help lost sailors back to shore. He particularly likes to swim near an island off the coast of Avantia.

According to its card, Sepron is 261 years old. It also has a power of 184, a magic level of 176 and a fright factor of 83.

Serpon is also the source of the serpent tooth a useful item that, when put into the magic shield, it makes the shield stop all incoming water. This is particularly useful in torrents or when battling water opponents.