From what I understand this can only be accomplished by the help of at least 1 deity?
Sages can able to travel the multiverses by entering Chidakasha.
There are three types of akasa (spaces): stula-akasa, chita-akasa and chida-akasa. We can view Sthula-akasa as physical space, Chitta-akasa as mental space/ space of thoughts, and Chidakasa as the space of consciousness.
Sthula-akasa is gross. It is the physical universe in which we live. It can be seen and experienced by all. The next one is Chitta-akasa, which is subtler and cannot be seen by the eyes. The last one is chid-akasa and is the subtlest of all. Chidakasa contains all possible physical universes. So, a yogin who can reach Chidakasa can able to travel to any universe.
It can be accomplished in several ways. Vicharana, Yoga, Dyana, Upasana are some primary paths for entering the chidakasa. If a person performs any one of them flawlessly then as a result of the sadhana she can enter into the multiverse. Her perception has to go beyond the physical, and the mental plane where Chitta vrittis cease to exist.
This has been explained in detail in the scripture named Yoga Vasista. A woman named Lila, who is a devotee of Saraswathi Devi performs fasting ritual for the well-being of her husband and as a result of the ritual the goddesses Saraswati allows Lila to enter into the Chidakasa, and then Lila can travel into two other universes. The important paragraph that contains all the details for traveling into the multiverse is given below
"His (Husband of Lila's) spirit is now roving in the sky, of which there are three kinds:—one the firmament or region of the sensible worlds; the other is the region of the mind, the seat of volition and creation; and the third is the region of Intellect, which contains the two others. Your husband's soul is now in the sheath of the region of Intellect; It is now by seeking in the region of the Intellect, that things which are inexistent here, are to be found there. As in passing from one place to another, you are conscious of standing in the mid spot, (which is neither the one nor the other); so you will arrive in an instant at the intermediate region of the intellectual world, (lying between this sensible and spiritual worlds). If you will abide in that intellectual world, after forsaking all your mental desires, you will certainly come to the knowledge of that spiritual Being who comprehends all in himself. It is only by your knowledge of the negative existence of the world, that you can come to know the positive existence of that Being, as you will now be able to do by my grace, and by no other means whatever."
In the given paragraph, the region of sensible worlds is Sthula-akasa, region of mind is Chitta-akasa, and the region of intellect is Chidakasa. Lila enters into the last one by the grace of Saraswathi, which is obtained due to her Upasana.