This one isn't really a ghost story, but I thought it was kind of cool.
One of my great uncles tells this story of a time when he was younger. Now he claims that he and his father-in-law (who later apparently died insane) had gotten involved in witchcraft. Not the mother goddess, faux-Celt, do no harm, let's make love to the soil kind, but the supremely ****ed up Latin American kind (a heady mix of Catholic mysticism, Nahuat beliefs and, of course, Satanism).
Apparently, when they met, his father-in-law was already a powerful and accomplished brujo or warlock and my great uncle, through courting his daughter, had gotten involved in his business. At first, the father-in-law didn't approve of my great uncle, thinking him to be a stupid oaf. Still, his daughter liked the boy, so he hatched a plan to get rid of him.
He invited my great uncle to his house in the hills to have a drink after he'd finished working for the day. Now, at this time, only the actual village had electricity and the roads leading to the capital were little more than dirt tracks for horses and carriages. The tracks to the hills were worse: steep, dusty, winding tracks through the forest that only donkeys, mules and pedestrians could traverse. Naturally, he made his trip in the dark and, having gotten lost more than once, had arrived late, much to the disapproval of the girl's father.
Up in the hills, the drink of choice was a powerful brew called chicha, something that people would drink out of bowls made from the bottom of gourds. There were several other people there and the drinking was already well under way. What they would do was fill the bowl, take a sip, and pass it along. The old man invited the boy to sit next to him in order to fulfill his plan.
When the old man received the drinking bowl, he took a sip and as he finished, sprinkled some powder into it. He did this in a subtle movement that my great uncle had luckily caught out of the corner of his eye. According to my great uncle, he'd later find out that it was a powerful spell that could turn a man's mind to mush and render him insane.
He was passed the bowl and suddenly all eyes were on him. Machismo dictated that he drink heavily of this vile brew and take it like a man lest he embarrass himself in front of all present and be known as a pansy forever. However, he already knew that the chicha was poisoned. Fortunately for him, all present had a habit of resting their machete blades on their chins as they drank (presumably so as to always have them at the ready, as these were untrusting, unsavoury and violent characters and drinking from these bowls was a two-handed job).
He put the bowl obstensibly to his lips, but actually let the liquid run down his machete to the ground. Those present were already too drunk to notice the wet dust at the base of the machete. They were also rather impressed that he drank the whole bowl in a single serving. The old man's plan was foiled.
On his way home that night, he got lost again and stumbled across a clearing. In this clearing was a coffin, just sitting there, on top of a bed of flowers. It was surrounded by four lit candles and my great uncle assumed that he had accidentally crashed a wake. He looked around for a house, but soon realised that this coffin was, indeed, sitting in a clearing in the middle of the forest.
Now, it's a very common belief that the dead should have a wake. Someone had to keep vigil over the deceased's body all night so that nothing would happen to their bodies before their souls ascended to heaven. My great uncle found a place to sit in the clearing and said to the coffin: "Well, it looks as though your family has abandoned you. Not to worry. I'll give you the wake you need."
He sat up and waited with the coffin in the dim light of the four candles until dawn broke. When he looked up and saw the sunrise though, a curious thing happened. He looked back at the clearing and the scene had changed. What he had taken to be a coffin sitting on a bed of flowers turned out to be a log sitting on some palm leaves. The four candles on each of the corners of the coffin were now empty coconut husks.
He started to get really frightened when he heard a voice coming from the forest. It was that of his prospective father-in-law. "You did well", the old man said, coming into view. "Most men would have been scared out of their minds when they saw the coffin. I can see that you are not a coward."
He ended up marrying the girl and the old man took him under his wing. Now he claims that he and his father-in-law would go out to the village cementery at night in order to perform different kinds of spells. They were apparently following instructions handed to the father-in-law by his own teacher that were written in a notebook. The old man was like a mystical Vegeta - obsessed with increasing his power.
The one I most vividly recall was the story about how they would catch toads and place them on some hot coals sitting in a magic circle. The toad wouldn't burn or try to hop away however, but suddenly get possessed by a demon and begin to speak. They would then ask it questions. Mostly gossip and hidden information about the sins of the people in the village, apparently.
The story of how the old man finally went bonkers was the one that creeped me out the most though. Apparently, there were various grades of brujo and to attain the final level, one had to successfully walk through a mirror onto the other side, then go back into the real world again.
Whether you did this physically or in some kind of astrally projected state, I can't recall. A very important point, apparently, was that you shouldn't actually look at anything while you're passing through. The story goes that he went into the mirror OK, but as he was going back out the other way, he (or his astrally-projected self) looked back into the mirror and saw something. Something seriously ****ed up.
My great uncle says he saw the Beast (or one of them, since there are two) that appears in the book of Revelation in the Bible. Whatever happened, the old man was never the same after that. He'd have his lucid periods that would sometimes last for weeks at a time, but the rest of the time, he'd run around naked, rubbing dirt on himself and babbling incessantly. When he was lucid, he'd tell everyone what had happened to him and beg them not to get involved in witchcraft.
That, apparently, was when my great uncle stopped doing it.