SB 3.20.44
siddhan vidyadharams caiva
tirodhanena so ’srjat
tebhyo ’dadat tam atmanam
antardhanakhyam adbhutam
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Then Lord Brahma, by his ability to be hidden from vision, created the Siddhas and Vidyadharas and gave them that wonderful form of his known as the Antardhana.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Antardhana means that these living creatures can be perceived to be present, but they cannot be seen by vision.