A class of non human beings generally described as non-human. They are mentioned with Devas, Rakkhasas, Dānavas, Gandhabbas, Kinnaras, and Mahoragas (? Nāgas).
Elsewhere AN.ii.38 they rank, in progressive order, between manussā and gandhabbā. They are of many different kinds: spirits, ogres, dryads, ghosts, spooks. In the early records, yakkha, like nāga, as an appellative, was anything but depreciative. Thus not only is Sakka, king of the gods, so referred to, MN.i.252 but even the Buddha is spoken of as a yakkha in poetic diction. MN.i.386 Many gods, such as Kakudha, are so addressed. SN.i.54 Of these above named, the followers of Vessavaṇa appear to be the Yakkhas proper. The term yakkha as applied to purisa is evidently used in an exceptionally philosophical sense as meaning “soul” in such passages as ettāvatā yakkhassa suddhi, Snp.478 or ettāvat’ aggam no vadanti h’ ekā, yakkhassa suddhim idha paṇḍitāse. Snp.875
The cult of yakkhas seems to have arisen primarily from the woods and secondarily from the legends of sea faring merchants. To the latter origin belong the stories connected with vimānas found in or near the sea or in lakes. Generally speaking, the Yakkhas were decadent divinities, beings half deified, having a deva’s supernormal powers, particularly as regards influencing people, partly helpful, partly harmful. They are sometimes called devatā SN.i.205 or devaputta. Some of these, like Indakūta and Sūciloma, are capable of intelligent questioning on metaphysics and ethics. All of them possess supernatural powers; they can transfer themselves at will, to any place, with their abodes, and work miracles, such as assuming any shape at will.
Sometimes the Yakkhas have been degraded to the state of red eyed cannibal ogres. The female Yakkhas (Yakkhinī) are, in these cases, more fearful and evil minded than the male. They eat flesh and blood and devour even men. DN.ii.346
Ordinarily the attitude of the Yakkhas towards man is one of benevolence. They are interested in the spiritual welfare of the human beings with whom they come in contact and somewhat resemble tutelary genii. In the Āṭānāṭiya Sutta, DN.iii.194f. however, the Yakkha king, Vessavaṇa, is represented as telling the Buddha that, for the most part, the Yakkhas believe neither in the Buddha nor in his teachings, which enjoin upon his followers abstention from various evils and are therefore distasteful to some of the Yakkhas. Such Yakkhas are disposed to molest the followers of the Buddha in their woodland haunts. Cp. the story of the Yakkha who wished to kill Sāriputta. Ud.iv.4 But the Mahā Yakkhas, DN.iii.204f. the generals and commanders among Yakkhas, are always willing to help holy men and to prevent wicked Yakkhas from hurting them. Among Yakkhas are some beings who are sotāpannas—e.g., Janavasabha, Sūciloma and Khara. The case of the Yakkha Vajirapāṇi is of special interest. D.i.95 He is represented as a kind of mentor, hovering in the air, threatening to kill Ambaṭṭha, if he does not answer the Buddha’s question the third time he is asked. In many cases the Yakkhas are “fallen angels” and come eagerly to listen to the word of the Buddha in order to be able to rise to a higher sphere of existence e.g., Piyaṅkaramātā and Punabbasumātā, and even Vessavaṇa, listening to Veḷukaṇḍakī Nandamātā reciting the Parāyana Vagga. AN.iv.63 At the preaching of the Mahāsamaya Sutta many hundreds of thousands of Yakkhas were present among the audience.
The names of the Yakkhas often give us a clue to their origin and function. These are taken from (a) their bodily appearance e.g., Kuvannā, Khara, Kharaloma, Kharadāthika, Citta, Cittarāja, Silesaloma, Sūciloma and Hāritā; (b) their place of residence, attributes of their realms, animals, plants, etc. e.g., Ajakalāpaka, Āḷavaka (forest dweller), Uppala, Kakudha (name of plant), Kumbhīra, Gumbiya, Disāmukha, Yamamoli, Vajira, Vajirapāṇi or Vajirabāhu, Sātāgira, Serīsaka; (c) qualities of character, etc. e.g., Adhamma, Katattha, Dhamma, Puṇṇaka, Māra, Sakaṭa; (d) embodiments of former persons e.g., Janavasabha (lord of men= Bimbisāra), Dīgha, Naradeva, Paṇḍaka, Sīvaka, Serī.
Vessavaṇa is often mentioned as king of the Yakkhas. He is one of the four Regent Gods, and the Āṭānāṭiya Sutta DN.iii.199ff. contains a vivid description of the Yakkha kingdom of Uttarakuru, with its numerous cities, crowds of inhabitants, parks, lakes and assembly halls. Vessavaṇa is also called Kuvera, and the Yakkhas are his servants and messengers. They wait upon him in turn.
No one, apparently, is free from this necessity of waiting upon the king even Janavasabba has to run errands for Vessavaṇa. DN.ii.207 The Yakkhas hold regular assemblies. DN.iii.201
It is sometimes difficult to decide whether the Yakkhas were non-humans spirits or aboriginal tribespeople. In the Vinaya, intercourse with yakkhas is forbidden. Vin.iii.37 Vin.iv.20