Calling on demons is generally inadvisable, but if you must, here are the best evil spirits to summon. Just be prepared - invoking demonic presences might cause the worst to happen.
Tales of hauntings and poltergeist activity after a summons aren't uncommon, nor are night terrors and sleep paralysis. People report hearing voices in mysterious ancient languages. The skin of summoners has been slashed and scratched during rites, and mysterious illnesses sometimes befall those who attempt to invoke known forces of darkness.
But if the urge is there, these are the demons to summon.
Baal, the Lord of the Flies, is the highest Christian demon one can summon, second only to Satan himself. He was once worshipped as a god, and many cities were named in his honor. Once he joined the ranks of Heaven's fallen angels, he was embraced by the underworld leaders and named one of the seven princes of Hell.
He often appears as an 8-foot-tall human, a cat, or a toad when invoked, and can supposedly render his summoner invisible upon request. Baal's powers are strongest in October; to call him into our realm, you’ll need black candles, a fern, and items made of either iron or gold.
Eligos rules 60 legions of demons in Hell. He's known for his strategic foresight and is adept at predicting enemy tactics and positioning. That comes in handy when summoners want to know the next move to make against adversaries.
Eligos is also able to assist his invokers in gathering support from high places for their cause. He is depicted as a ghostly knight, riding a semi-skeletal, demonic horse known as the Steed of Abigor. The horse is itself a minion of Hell, created from the remains of a horse from the Garden of Eden. Baal gave the steed to Eligos as a gift. This highly-respected demon is strongest in early June; to summon him, you will need thyme, copper, and yellow candles. Schedule a daylight ceremony, too.
According to Pseudomonarchia Daemonum, Agares appears as an old falconer on the back of a monstrous reptile. This demon teaches its conjurer new languages and helps them acquire a high rank in their chosen profession.
Agares is best summoned in late March; perform the ceremony in daylight while burning blood-red candles. Gifts of carnations and copper items help welcome Agares into our world.
This dark soul is commonly referred to as "the President of Hell." In human form, he appears as a blond, teenage youth with a brooding face. A rebellious demon, Glasya-Labolas is equipped with a monstrous ability to incite aggression. He's also incredibly intelligent, having studied the ancient wisdom of his people, and knows the secrets of the occult as well as our own earthly sciences.
Summoners seeking the heights of wisdom shouldn't be too demanding of Glasya-Labolas; he has a hair-trigger temper and will damn someone’s eternal soul without a second thought. This demon is best invoked in late July using rosemary, yellow candles, gold items, and plenty of daylight.