Siddhi-Mystical powers
Mystical supernatural powers are called siddhi (Devanagari: सिद्धि ISO15919: siddhi). This Sanskrit word which also means perfection. So, attaining any of these psychic powers is also called siddhi.
There are many kinds of siddhis. All siddhis, which are attainable by jeev, can be classified into three categories
These are discussed below and finally the assessment of if these siddhis are beneficial.
Tamas Siddhi

Tamsi Siddhi (Devanagari: तामसी सिद्धि ISO15919: tāmasī siddhi) is attained through the worship of ghosts, by meditating at the cremation-grounds after midnight.
This siddhi is used to fulfill one’s own selfish motives, by torturing others.
Those who practice these siddhis after death they are sent to Narak to atone for their sins.
Rajas Siddhi
Our scriptures assert that Rajas siddhi (Devanagari: राजस सिद्धि ISO15919: rājasa siddhi) is the science of liberation. It is the outcome of practicing the knowledge of Tantra and is attained by the grace of Goddess Kali.
The word Tantra is defined in Tantra Sanghita as a combination of two Sanskrit words tanoti (Devanagari: तनोति ISO15919: tanōti) and trayate (Devanagari: त्रयते ISO15919: trayatē).
It means the science of expansion of spiritual knowledge and mukti. Since this is influenced by rajas guna, in its truest form it is not evil. Unfortunately, many selfish, impious people attain these powers. Then instead of using them for spiritual advancement they abuse these powers for obtaining worldly things for their own benefit.
Still, comparatively speaking Rajasi siddhis is better than Tamasi Siddhi.
Sattvik Siddhi
Sattvik siddhi (Devanagari: सात्त्विक सिद्धि ISO15919: sāttvika siddhi) is attained by following the path of yoga and are bestowed by devi-devata. There are eight types of sattvik siddhis.
Anima
i. Anima siddhi (Devanagari: अणिमा सिद्धि ISO15919: aṇimā siddhi) enables it's master to become tinier than the tiniest particle.
Laghima
ii. Laghima siddhi (Devanagari: लघिमा सिद्धि ISO15919: laghimā siddhi) enables it's master to become lighter than feather.
Mahima
iii. Mahima siddhi (Devanagari: महिमा सिद्धि ISO15919: mahimā siddhi) enables it's master to become heavier than a mountain.
Prapti
iv. Prapti siddhi (Devanagari: प्राप्ति सिद्धि ISO15919: prāpti siddhi) enables it's master to procure anything from anywhere in the entire universe.
Ishittva
v. Ishittva siddhi (Devanagari: ईशित्व सिद्धि ISO15919: īśitva siddhi) provides the ability to make the impossible, possible within the material world. The holder of this power can even create a new swarg.
Vashittva
vi. Vashittva siddhi (Devanagari: वशित्व सिद्धि ISO15919: vaśitva siddhi) enables it's master to control anything and anyone in the world.
Prakamya
vii. Prakamya siddhi (Devanagari: प्राकाम्या सिद्धि ISO15919: prākāmyā siddhi) enables it's master to fulfill all their material desires.
Kamavashayita
viii. Kamavashayita siddhi (Devanagari: कामावशायिता सिद्धि ISO15919: kāmāvaśāyitā siddhi) enables it's master to fulfill their resolutions instantaneously.
Are Sattvik Siddhis good?
Sattvik siddhis on the surface seem very attractive and even divine. But they are not.
Devi-Devatas in swarg bestow the sattvik siddhis. They too are material beings like all of us. They have many more powers than humans. Still, since they are under the control of Maya their powers are limited and material in nature. So, when they bestow the siddhis on a jeev the siddhis are also limited in nature.
So, beware! Demonstrating miracles with these sattvik siddhis does not prove any divinity.
The one and only goal of every material being is self-happiness. These demonstrations are a trick merely to attract faith of gullible innocent people to fulfill one's own desires.

All these Sattvic siddhi seem wonderful, but they are dangerous for both the possessor and the spectator.
The dangers for the possessor of these siddhis include the following:
1. The possession of these mystic powers creates uneasiness even in the hearts of the yogis.
2. The possession of these powers inflates the ego, ultimately leading to an aspirant's spiritual downfall. God loves humility.
3. The power of these siddhis diminishes with each use and eventually gets all used up.
These siddhis are equally harmful for those who witness the performance of miracles using these powers or benefit from these.
The rationale is simple: when ordinary material beings, experience the miracle of these psychic powers, they consider the yogi (i.e. the possessor of these siddhis) to be equal to God, thereby developing faith in the yogi and following his teachings. This wrongful assumption and faith ultimately leads to the aspirant’s spiritual downfall.
Thus, one should realize that sattvik guna is also a mode of maya, and all these sattvic siddhis are material powers. Attaining them and witnessing prove detrimental to spiritual progress.
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