A class of non human beings generally described as amanussā. They are mentioned with Devas, Rakkhasas, Dānavas, Gandhabbas, Kinnaras, and Mahoragas (? Nāgas) (E.g., J.v.420).
In other lists (E.g., PvA. 45, 55) they range immediately above the Petas; in fact, some of the happier Petas are called Yakkhas. Elsewhere (E.g., A.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 nāgā, as an appellative, was anything but depreciative. Thus not only is Sakka, king of the gods, so referred to (M.i.252; J.iv.4; DA.i.264), but even the Buddha is spoken of as a yakkha in poetic diction (M.i.386). Many gods, such as Kakudha, are so addressed (S.i.54).
According to a passage in the Vimānavatthu Commentary, (VvA.333) which gives illustrations, the term is used for Sakka, the Four Regent Gods (Mahārājāno), the followers of Vessavana, and also for puriso (individual soul?). In the scholiast to the Jayadissa Jātaka (J.v.33), the figure of the hare in the moon is also called yakkha. Of these above named, the followers of Vessavana 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 (SN.vs.478), or ettāvat' aggam no vadanti h' ekā, yakkhassa suddhim idha pānditāse (SN.vs.875).
In the Niddesa (MNid.282), yakkha is explained by satta, nara, mānava, posa, puggala, jīva, jagu, jantu, indagu, manuja. The last term is significant as showing that yakkha also means "man."
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. The worship of trees and the spirits inhabitating them is one of the most primitive forms of religion. Some, at least, of the yakkhas are called rukkha devatā (E.g., J.iii.309, 345; Pv.i.9; PvA.5) (spirits of trees), and others bhummadevatā, (PvA.45,55) (spirits of the earth), who, too, seem to have resided in trees. 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 (E.g., S.i.205), or devaputta (E.g., PvA. 113, 139). Some of these, like Indakūta and Suciloma, 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. An epithet frequently applied is mahiddhika (E.g., Pv.ii.9; J.vi.118). Their appearance is striking as a result of former good kamma (Pv.i.2, 9; ii.11; iv.3, etc.). They are also called kāmakāmī, enjoying all kinds of luxuries (Pv.i.3), but, because of former bad kamma, they are possessed of odd qualities, thus they are shy, they fear palmyra leaf and iron. Their eyes are red and they neither wink nor cast a shadow. J.iv.492; v.34; vi.336, 337; these various characteristics are, obviously, not found in all Yakkhas. The Yakkhas are evidently of different grades - as is the case with all classes of beings – the highest among them approximate very nearly to the devas and have deva-powers, the lowest resemble petas. The Yakkhas are specially mentioned as being afraid of palm leaves (J.iv.492).
Their abode is their self created palace, which is anywhere, in the air, in trees, etc. These are mostly ākasattha (suspended in the air), but some of them, like the abode of ālavaka, are bhumattha (on the ground) and are described as being fortified (SNA.i.222). Sometimes whole cities e.g., ālakamandā stand under the protection of, or are inhabited by, Yakkhas.
In many respects they resemble the Vedic Pisācas, though they are of different origin. They are evidently remnants of an ancient demonology and have had incorporated in them old animistic beliefs as representing creatures of the wilds and the forests, some of them based on ethnological features. (See Stede: Gespenstergeschichten des Petavatthu v.39ff ).
In later literature 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 (J.iv.549; v.34); and devour even men (D.ii.346; J.ii.15ff.) and corpses (J.i.265). They eat babies (J.v.21; vi.336) and are full of spite and vengeance (DhA.i.47; ii.35f.). The story of Bhūta Thera is interesting because his elder brothers and sisters were devoured by a hostile Yakkha, so the last child is called Bhūta to propitiate the Yakkha by making him the child's sponsor!
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 Atānātiya Sutta (D.iii.194f), however, the Yakkha king, Vessavana, 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 (a list in D.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, Suciloma and Khara (s.v.). Some Yakkhas even act as messengers from another world, and will save prospective sinners from committing evil (Pv.iv.1). The case of the Yakkha Vajirapāni is of special interest. D.i.95. The Commentary (DA.i.264) says he is not an ordinary Yakkha, but Sakka himself.
He is represented as a kind of mentor, hovering in the air, threatening to kill Ambattha, 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., Piyankaramātā and Punabbasumātā, and even Vessavana, listening to Velukandakī Nandamātā reciting the Parāyana Vagga (A.iv.63). At the preaching of the Mahāsamaya Sutta (q.v.) many hundreds of thousands of Yakkhas were present among the audience.
It has been pointed out (Stede, op. cit) that 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, ālavaka (forest dweller), Uppala, Kakudha (name of plant), Kumbhīra, Gumbiya, Disāmukha, Yamamoli, Vajira, Vajirapāni or Vajirabāhu, Sātāgira, Serīsaka; (c) qualities of character, etc. e.g., Adhamma, Katattha, Dhamma, Punnaka, Māra, Sakata; (d) embodiments of former persons e.g., Janavasabha (lord of men= Bimbisāra), Dīgha, Naradeva, Pandaka, Sīvaka, Serī.
Vessavana (q.v.) is often mentioned as king of the Yakkhas. He is one of the four Regent Gods, and the ātānātiya Sutta (D.iii.199ff) contains a vivid description of the Yakkha kingdom of Uttarakuru, with its numerous cities, crowds of inhabitants, parks, lakes and assembly halls. Vessavana is also called Kuvera, and the Yakkhas are his servants and messengers. They wait upon him in turn. The Yakkhinīs draw water for him, and often are so hard worked that many die in his service. E.g., J.iv.492. Mention is also made (e.g., DA.ii.370) of Yakkhadāsīs who have to dance and sing to the devas during the night. Early in the morning they drink a cup of toddy (surā) and go off into a deep sleep, from which they rise betimes in the evening ready for their duties.
No one, apparently, is free from this necessity of waiting upon the king even Janavasabba has to run errands for Vessavana (D.ii.207). Among the duties of Vessavana is the settling of disputes between the devas, and this keeps him (J.vi.270) much occupied. In this work he is helped by the Yakkhasenāpati, whose business it is to preside over the courts during eight days of each mouth (SNA.i.197). The Yakkhas hold regular assemblies on Manosilātala on the Bhagalavatīpabbata (SNA.i.187; cp. D.iii.201 and DA.iii.967). As followers of Kuvera, lord of riches, the Yakkhas are the guardians and the liberal spenders of underground riches, hidden treasures, etc., with which they delight men. E.g., Pv.ii.11; PvA.145; Pv.iv.12; PvA.274. These were seven yakkhas who guarded the wealth of Jotiyasetthi (DhA.iv.208f.).
It is difficult to decide whether the Yakkhas, who are the aborigines of Ceylon (Lankā), were considered human or non human. Kuvenī, one of their princesses, and her maid, can both assume different forms, but Vijaya marries Kuveni and has two children by her. (Cp. Vin.iii.37; iv. 20; where sexual intercourse with a Yakkha is forbidden). The Yakkhas are invisible, and Vijaya is able to kill them only with the help of Kuveni (Mhv.vii.36); but their clothes are found fit for Vijaya and his followers to wear (Mhv.vii.38). Again, Cetiyā (q.v.) could make herself invisible and assume the form of a mare, but Pandukābhaya lived with her for four years and she gave him counsel in battle. Later, when he held festivities, he had the Yakkha Cittarāja on the throne beside him (Mhv.x.87). In all probability these Yakkhas were originally considered as humans, but later came to be confused with non humans. Their chief cities were Lankāpura and Sirīsavatthu.
The commonly accepted etymology of Yakkha is from the root yaj, meaning to sacrifice. Thus: yajanti tattha balim upaharantī ti yakkha (VvA.224), or pūjanīyabhāvato yakkho, ti uccati (VvA.333).