The reason many Dzogchen teachings are connected to a sadhana involving the peaceful and wrathful deities is that the displays include these deities. The practice lets whatever is already present within you become visible; nothing else manifests. Since the peaceful and wrathful deities are already present within your body, they become visible during Tögal practice. The deities in Tögal are the same ones that will appear in the bardo. So, if the complete mandala has manifested during your life, no second mandala needs to appear in the bardo state—it doesn’t manifest twice. This is why many Dzogchen teachings emphasize the mandala of the peaceful and wrathful deities.
Spoken by Tulku Urgyen Rinpoche