Rudra

Rudra (Tib. རུ་དྲ་, Wyl. ru dra) is a demon who embodies egohood.

Explanation

Khenpo Namdrol explains^[1]: In general there are three ways to explain rudras.

The first identifies them as the Wrathful Herukas in the Akanishtha pure realm, who stand on top of the bodies of different beings in order to subjugate them. However, these are in fact sambhogakaya manifestations, despite having the name ‘rudra’ applied to them.
The second are emanations emitted by buddhas and bodhisattvas, nirmanakaya manifestations who appear in the ‘fields’ of those needing training, in accordance with that particular field. In addition to emanations like Shakyamuni, there are also those who are outwardly disruptive, such as the disorderly monks emanated by Shakyamuni so that their transgressions could be used as an example of how not to act, and so become the basis for the rules of monastic discipline. However, these too are essentially pure emanations. These two types of rudra can therefore actually become objects of refuge.
The third type of rudra is essentially negative, and is a tangible being, reborn in a malignant form as a result of broken tantric commitments in previous lives. Such a rudra is usually accompanied by a retinue of other malignant beings, and as a group their main activity is to cause obstacles to the propagation of the teachings of the secret mantrayana.