In Tibetan Buddhism, there are Dharma protectors who are both enlightened and not enlightened. These Dharma protectors, in turn, can take on both peaceful and wrathful forms. Enlightened Dharma protectors are more special because they can also take the form of an unenlightened being who acts and appears to be unenlightened but in reality, they are, while the unenlightened Dharma protectors cannot take the form of an enlightened Dharma protector.
Examples of enlightened Dharma protectors that take on the forms of unenlightened beings are Kalarupa and Palden Lhamo, who are mamo in form but who are Manjushri and Saraswati in nature. Other Dharma protectors that appear to be very convincing worldly protectors are Tsui Marpo, Dorje Setrab and Achi Chokyi Drolma (also known as Lhamo Apchi). These special category of Dharma protectors have been confirmed as enlightened by many different accomplished Lamas, although there are still many who think otherwise. These very convincing worldly Dharma protectors on first glance may seem worldly, but upon further examination, they are enlightened, based on their origin story, iconography and testimonials from various masters.
The question is, why would an enlightened deity take the form of a spirit when they could very well remain as Buddhas? The main reason is, most of us are unable to perceive or receive help from a Buddha or a Yidam directly, due to the lack of merits that ordinary people have. Only a Buddha can perceive another Buddha directly, or at least, someone who has cultivated to that level and most of us have not, therefore, the direct form of a Buddha is out of reach for most of us. Due to this, the ever compassionate Buddha has to use other methods to reach out to us and emanate sometimes evn in the form of spirits, which are closest to our realm but can do much more than what a human can do as they are not restricted to having a physical form. This is the reason why most Dharma protectors, either enlightened or unenlightened take the form of a spirit, more than anything when appearing to us. It does sound a bit far fetched, but it is entirely possible as Trijang Rinpoche quotes the scholar Chandrakirti:
“Furthermore, to the common view of beings, it is difficult to fully understand the appearances of holy great Aryas and their inconceivable three secrets at the definitive level. Although Buddha Shakyamuni was free of all dangers, Devadatta firing his catapult at him, wounding him, and he constantly appeared to compete with and harm Buddha by setting mad elephants upon him and so forth. Yet glorious Chandrakirti in his Lamp Illuminating Guyasamaja quotes from the Great Union Tantra called Uncommon Secrets, as follows,
Then, I shall furthermore expound upon the Omniscient One's perfect entourage. It is like this: Manjusri became King Shuddhodana. Avalokiteswara became Devi Maha Maya. Sri Devi is Yasodhara. Vajrasattva is Rahula. Sarva Nivarana Viskambini is Shariputra. Samantabhadra is Stavira Ananda. Indra, Lord of the Gods, is Stavira Devadatta. Great Vairochana is Samyaksam Buddha Glorious Shakyamuni. By this principle, Buddha emanates as both the one around whom the entourage gathers, as well as the entourage, in order to get sentient beings who are beginners started.
Thus, Devadatta was, himself, said to be an intentional emanation of the Lord of the Gods, Indra. “
Tsui Marpo
