Source: TW
Few things about diksa which most do not know and this ignorance is misused by some to scare people.
tantra recommendations
In tantra the most recommended diksha is abhiseka diksha (shakta-pUrNa-krama etc etc). This is mandatory when doing karmakanda of Mahavidya. Why? Because this diksa is an elaborate puja asking protection and aid as well for the upasaka.
Most of the small orgs or people selling diksas have no idea, nor the adhikara to give a shaktabhiseka diksa .. for to do this one must have attained at least a pUrNAbhiseka-diksha himself. So what passes off as diska today in many small places is just some random hodgepodge created with zero base from tantra shastras.
Before diksha comes upadesha. The guru or uttara sadhaka can give upadesa of a mantra by which someone is eligible to chant the mantra.
After shaktAbhiseka the sadhaka is eligile to full scale tantra puja of the deity.
The tantra-s also mention only for Mahavidya karmakanda abhiseka diksha is needed, for other deities (even Bhairava) a much simpler upadesam can work from a competent source/ guru-figure can work.
Why dIxA?
There are 1000s of people who engage with fierce deities with simple bhakti… be it kali or tara or nrsimha.. and some positivity easily comes to their lives. Both Kali and Tara are Mahavidya and yet there is perhaps no home in eastern India which does not have some photo of simple bhakti to them. It is perfectly okay and good to do.
So why diskha? That comes to play when mantra siddhi and karmakanda is to be done by the individual. Specially when bija mantras are involved.
Therefore, a nama mantra like Om Bhairavaya Namah needs just upadesa from a source, and shraddha of the upasaka, to work.
Those few who are destined to go into tantric karmakanda, will get a shaktabhiseka to proceed. But just like thousands doing simple name of kali or tara in Eastern india, or even Nrsimha (ugra forms) are doing perfectly fine and benefitting, same way with this.
Finally the result is the proof. In 3 years innumerable thousands and thousands have done this japa and overwhelming majority benefitted spiritually (and in many cases materialistically too) with this simple japa.
Therefore, correct knowledge about diksa, whether mandatory or not, upadesa, differences between the two etc are important, so people dont get mislead.
Om Bhairavaya Namah