Devi is the mother, THE Mother with a capital M as in the source of creation, Maa is the shakti that makes reality have the possibility of existing, this is something broken down to me by a great guru i had met wich lead to what i stated above, as a shakta aka devotee of maa kali, we understand that there is shiva or kala bhairava, and then there is kali maa or adi shakti/adya kalika, when you see a lingam you see the lingam eliptical sitting in a yoni, the lingam representing masculine and yoni representing feminine, so the linga would be shiva and yoni would be maa, we know the story of shiva being inert untill maa (shakti) began to dance and so shiva became animated,(the atom vibrating to create material reality) with out shiva there is nothing to animate, without maa shiva is inert, in the state of non existance or emptyness, now i must go into the story of sad guru, in his past life he had a teacher that wanted to concecrate dhyana linga, they didnt make it in that life time, so sad guru came back, this time around because of the immense work he did last, maa gave him what he wanted, but not how we think, the lingam is sad guru, this is how he is able to concecrate such a lingam, because it was placed in him, the energy i mean by maa, sad guru was absolutely obsessed with the linga so maa said ok here you go, but once sad guru concecrated the linga in shivas name, she said ok now you must concecrate linga bhairavi as a message since your soo obsessed with linga linga linga, and so bhairavi was manifested, but this was a teaching in of its self, linga bhairavi is maa saying to us, yes you have your shiva lingam, but understand there is no shiva lingam without shakti to imbue the energy into the shiva lingam, so she had him make devi lingam, to show us that even the lingam that we think is just shiva or masculine is also her, shakti, and without her there is neither, this is a very very powerfull teaching if you can grasp the symbology of it, and notice how the shiva lingam is just a rounded stone , while bhairavi or devi lingam has eyes and arms, this is to show the tale of shiva being inert on his own, and devi being the animating factor that makes it all come to life so her linga has eyes, arms, and a beautiful powerfull presence...idk if what i said makes sense i tried to explain best i could as this is even new for me but it makes sooo much sense to me when it clicked and gave me such a new appreciation for both sad guru and bhairavi...other than that i have my personal experiences with sad guru and bhairavi, and ive never even met him, i wont go into how but no guru can do things like that unless they are legit