Because this is the age of Kaliyuga, the demonic forces are everywhere, but they run away from those places where pure mantras are chanted. For example, as related in the Valmiki Ramayana, Lord Rama once was asked by a ghost, “O Lord, we are also Your creation. We also need a place to live and enjoy. Please tell us what and where can we enjoy?” The Lord replied, “Wherever My glories are not chanted, that’s where you should live, and the money of those who do not give charity to please Me, that is the wealth for you to enjoy.” Incurable chronic diseases, lingering court cases, devastating fires, all categories of accidents, ferocious quarrels and fights without apparent reasons- many of these types of difficulties are caused by evil spirits or ghosts. They take advantage of such situations and enjoy bringing suffering to people. Humans with such attitudes, who like to enjoy people’s suffering or who cannot tolerate others’ self-improvement, become evil spirits after their death.
However, in Vraja, everyone is engaged in glorifying and worshiping Lord Krsna with the chanting of sacred mantras; as Niti Sastra says, mantradhinam ca daivatam, “The Lord is controlled by mantras.” Mantra chanting purifies the heart and mind. It invites the Lord to come, participate, and give blessings so the evil spirits will leave.
As it is stated in the Valmiki Ramayana:
na tatra danavah santi na pisaca
na raksasahyaksa kinnara vetala bhuta
preta vinayakahyatra devo grhe
visnuh kirtyate hi sada satam
“Wherever there is worship of Lord Visnu, or glorification of Him, there the demons who look like humans, the hobgoblins, the ferocious-faced demons, the semi-demigods, the demons with undesirable features, the vamipires, the ghosts, the evil spirits or any other such beings cannot live.”
Vedic civilization is in no way polytheistic, but misinformed people often misconstrue Vedic civilization as polytheistic. Vedic civilization is vast, thus scrutiny of the scriptures is needed to understand that there is only one God in charge of everyone and everything. All other superhuman entities are either expansions of the Supreme God or entities given super powers from Him to manage the various universal affairs. A layman that studies Vedic philosophy without the right teacher may conclude that it is a polytheistic philosophy, but Vedic philosophy is monotheistic, based on real love for the one Supreme God who reciprocates with those who love Him.
[Visnu Purana 5.2.4]
“When the source of Visnu and His plenary portions appeared upon the earth, all the auspicious attributes of the seasons arrived along with Him.”
Even though Krsna took birth in the middle of the rainy season still all inauspicious symptoms of the rainy season were driven away by His birth. Out of all the seasons of the year, the months of the rainy season are said to be the most inauspicious. But upon this particular occasion they became super-charged with all good qualities and, thus, actually became better than other seasons. As witnessed by the above quotation, Lord Krsna is not an incarnation of Visnu- rather, He is the source of all incarnations. Chant the Mahamantra, the Holy Names of the Lord:
Hare Krishna Hare Krishna
Krishna Krishna Hare Hare
Hare Rama Hare Rama
Rama Rama Hare Hare
[Sri Krsna Balaram Swamiji, KBS5139]