"Samhain was the Celtic God of the Dead, worshipped by the Druids with dreadful bloody sacrifices at Halloween."
As for Samhain being the "lord of the dead," this is a gross fallacy that seems to have been perpetuated in the late 18th and 19th centuries. There is no historic or archeological evidence of any Celtic deity of the dead named "Samhain." The names of about 350 Celtic deities are known and Samhain is not found among them. The Dictionary of the Gaelic Language says that "samhuinn" (the Scots Gaelic spelling> means "summers end."

"Halloween is a rite with pagan, demonic roots."
Halloween did not originate as a Satanic festival, but was religious in nature (the Celtic faith of the ancient Druids). The Celts did not actually have demons or the devil in their belief system. Halloween's association with Satanic worship is a modern phenomenon. There is a big difference between Paganism and Satanism. Pagans are people who believe in more than one god. Some modern day pagans call themselves "Wiccans." Pagans do not worship Satan or the devil. Pagans believe in powers (spirits and gods) which they "ask" to do things.

Satanists are worshippers of Satan. They believe in Satan and demons which they "demand" to do things. The Celts were pagans, not Satanists. There is no original evidence to indicate that Samhain was any more Satanic than pagan harvest festivals of other religions, like the Romans or the Greeks. The Celts did believe in gods, giants, monsters, spirits, fairies, and elves, but these were not considered evil ... so much as they were dangerous. The fairies, for example, were often considered hostile and menacing to humans because they were seen as being resentful of men taking over their lands. On the night of Samhain, the fairies would sometimes trick humans into becoming lost in the numerous fairy mounds, or "sidhe," where they would be trapped forever.

"Evil Druids would go from castle to castle, seeking virgin princesses to rape and sacrifice to the "lord of death," leaving carved pumpkins illuminated by candles (made from human fat) for those who cooperated, and arranging demonic assassinations for those who refused to give them what they wanted."
There is absolutely "no" evidence anywhere (from tradition, Celtic texts, or archaeology) that these events ever occurred.

There is a general agreement among historians that the Celts did in fact practice some form of human sacrifice, but then, most cultures at that stage of development did. The Celts sacrifices seem to have been limited to criminals, prisoners-of-war, or volunteers. Today, we still sacrifice humans, mostly "criminals," but we now call it the "death penalty."

The finds in the peat bogs of apparent human sacrifices (or judicial killings) are mostly in Germanic territories, not Celtic.

The pumpkin is a New World plant that never grew in Europe until modern times, so it could not have possibly ever been used to make "carvings illuminated by candles."