In Esoteric Buddhism, Tantric rituals often involve the invocation of various deities through visualizations and mantras. These deities are seen as embodiments of different aspects of the ultimate reality and are believed to possess great power and wisdom.

The first step in invoking these deities is through the use of a mandala, a sacred geometric diagram that represents the universe. The mandala serves as a visual aid for the practitioner to focus their mind and energy on the deity they wish to invoke.

Once the mandala is set up, the practitioner will then begin the process of visualization. This involves mentally visualizing the deity in front of them, in all their glorious and powerful form. This visualization is not just a static image, but rather a dynamic process where the deity is seen as alive and interacting with the practitioner.

As the visualization becomes more vivid and detailed, the practitioner will then begin to recite mantras, which are sacred sounds or phrases that are believed to have the power to invoke the deity. These mantras are often chanted or repeated in a specific rhythm and tone, which helps to further deepen the practitioner's focus and connection with the deity.

As the practitioner continues to recite the mantras, they may also engage in mudras, which are hand gestures that symbolize different aspects of the deity's power and teachings. These mudras are believed to help channel the deity's energy and bring it into the practitioner's body and mind.

Through the combination of visualization, mantras, and mudras, the deity is believed to be fully invoked and present in the ritual space. The practitioner then engages in various offerings and praises to the deity, expressing their devotion and gratitude for their presence.

The ultimate goal of invoking these deities is to merge with their divine energy and wisdom, and to gain insight and understanding of the ultimate reality. By engaging in these Tantric rituals, practitioners hope to transcend their individual selves and connect with the universal truth and enlightenment.

In conclusion, the invocation of deities in Tantric rituals involves a deep and intricate process of visualization, mantras, and mudras. Through these practices, the deities are believed to be fully present and their power and wisdom can be accessed by the practitioner.