The word 'Seth' was first said as 'Set'. Because of changes in the Egyptian language over the 3,000 years that Seth was worshiped, the 't' in Set was pronounced so similarly from 'th' that the Greeks wrote it as Seth during the Ptolemaic period. Seth was originally responsible for protecting Ra during his journey in the afterlife, personally slaying the great serpent Apep. Later, Seth killed his brother Osiris who had succeeded Ra out of jealousy. Horus(Osiris and Isis' son) eventually defeated Seth and claimed the throne.
Seth had three siblings. His brother was named Osiris and his sisters were named Isis and Nephthys who was also his wife. He also had a nephew Horus. Nephthys married Seth and Isis married Osiris. Seth and Nephthys had a son named Anubis. His father and mother were Geb and Nut respectively.
Seth was the god of desert storms and thunder. His color is red which represented evil in Egypt. He also possessed people when he wanted to.
Seth is often shown as a mysterious and unknown creature called the Set Animal.The Set Animal had a curved snout, square ears, dog-like body, forked tail, red eyes and red hair. Set could control this animal and would use it to destroy his enemies.