In my opinion, a lot of deities do that. Are you having an affinity toward any specific deity? Unlike a spell, deities are more of a long-term commitment. Generally, we have one of the main deities as our patron deity, and other deities are invoked from time to time for specific purposes. It is our main deity that always guides us and protects us from omissions and faults, shapes our life path in the best possible way as this deity now represents the awakened mind of oneself.
Sometimes it can be confusing between Hindu and Buddhist deities due to historical contests between Buddhists and Hindus in medieval times who competed for royal patronage. Buddhists modeled a lot of their deities after the ancient Hindu deities, or absorbed them as is, declaring them as having been subjugated and enlightened by the Buddha haha. And then, after Buddhism declined in India, some of the Buddhist deities were re-absorbed back into the Hindu pantheon. And Buddhist pantheon also absorbed some of the local Tibetan Bon deities as well as Daoist deities, again calling them either protectors or using the same story - Buddha enlightened them. I talk here of assimilation of local deities into Buddhism only about India (where Buddhism originated) and Tibet (as I am a student of Tibetan Buddhism), but similar stuff happened in Burma, Thailand, China, Japan, etc.
Buddhist Tara is, for the most part, Hindu Durga
Buddhist Vajrapani is nothing but Indra (Yellow Emperor)
Buddhist Vajradhara is also derived from Indra
Buddhist Nilakantha is derived from Shiva and so on
Amongst Indian deities, there are three main categories: Eurasian Vedic deities, the aboriginal Native deities (like Kumara or Skanda), and Tribal Deities (who are now absorbed by the Hindu pantheon). We today regard all of them as Hindu deities.
In my experience, some are ancient, immortal entities or their manifestations (like Shiva, Kali, Vishnu, Ganesha, etc.), and others are egregores created and maintained by the faith of the millions (like Yahweh and to an extent, Jesus) - my personal preference is the first category although the second one can provide results too (like Dream’s Exorcism audio). There is also a huge world of Egyptian, African, and pre-Abrahamic European deities which one can explore - preserved by today by Bushmen, Shamanic and Occult traditions (to an extent).
How do we choose a deity traditionally?
- The first option would be based on affinity - I just knew it is the Great Goddess for me, I have always known as she is with me for many lifetimes.
- The second one would be based on one’s Teacher’s guidance - an accomplished teacher will consider various aspects, including the horoscope of the student, etc., and suggest a deity/mantra (not all mantras are suitable for everyone. Some mantras are ari (foes) while others are mitra (friends).
- The third option would be based on a specific need - healing, protection, wealth, manifestation, etc. (guiding the life is a generic requirement
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People who want something simple, do not want to go through initiations, etc. can always recite the Green Tara mantra. Tara is known as the Mother of All Buddhas. Or, if you are more into male forms, the easiest choice would be Ganesha, the elephant-headed wisdom deity.