Samhain can be summoned by a powerful witch through "3 blood sacrifices over 3 days, the last on the final day of harvest," which is the 31st of October, Halloween's Eve. Once Samhain has risen, he is able to raise ghosts, zombies, and ghouls and unleash them onto the world. He is also able to emanate an explosive light from his hands, in which Sam is also immune too.

The myth of Samhain, the "Celtic God of the Dead" was born in the 19th century by Christians, meant to "demonisize" the Pagan celebration of Samhain. The creation of Samhain as a Celtic God can be traced back to a book by Godfrey Higgins in 1827 in which he tried to prove that the druids originated in India (Higgins referenced Samana, a Hindu/Vedic deity, God of the Dead.) The first reference though came from a man called Vallency, who mentioned the name in the late 18th century.

The word Samhain is derived from Old Irish and refers to the first of November. The proper pronunciation, according to the Oxford English Dictionary, is /ˈsaʊɪn/ or /ˈsawɪn/. Samhain is the Festival of the Dead and symbolizes the end of the summer and the Celtic New Year. Traditionally, it was the day of the last harvest and the time to take inventory of live stock to be slaughtered.

According to Celtic lore Samhain is the time of year when the boundaries between the worlds of the living and the dead become transparent, allowing supernatural beings to pass between the worlds. Usually, it's the time of year where ancestors were especially honored (see "All Saints' Day). The Samhain Festival involved bonfires, as well as costumes and masks to disguise the living and make them mimic the evil spirits that walked the earth on Samhain.

Many Halloween traditions come from Irish and Scottish Lore - the carving of the pumpkins and lighting candles inside of them, the disguising as supernatural or evil creatures, the fireworks and bonfires. Trick-or-Treating derives from the tradition of Mischief Night. At Hollywood parties, typical games are dunking for apples or eating strung up scones without the use of hands.