The tenth mandala of the Rigveda has 191 hymns. Together with Mandala 1, it forms the latest part of the Rigveda, containing much mythological material, including the Purusha sukta (10.90) and the dialogue of Sarama with the Panis (10.108), and notably containing several dialogue hymns. The subjects of the hymns cover a wider spectrum than in the other books, dedicated not only to deities or natural phenomena, including deities that are not prominent enough to receive their own hymns in the other books (Nirrti 10.59, Asamati 10.60, Ratri 10.127, Aranyani 10.146, Indrani 10.159), but also to objects like dice (10.34), herbs (10.97), press-stones (for Soma, 10.94, 175) and abstract concepts like liberality (towards the rishi, 10.117), creation (10.129 (the Nasadiya Sukta), 130, 190), knowledge (10.71), speech, spirit (10.58), faith (10.151), a charm against evil dreams (10.164).
10.15, dedicated to the forefathers, contains a reference to the emerging rite of cremation in verse 14, where ancestors "both cremated (agnidagdhá-) and uncremated (ánagnidagdha-)" are invoked.
10.47 to 50 are to Indra Vaikuntha, "Indra son of Vikuntha". Vikuntha was an Asuri whom Indra had allowed to become his second mother. The rishi of 10.47 is called Saptagu, while that of 10.48-50 is likewise called Indra Vaikuntha.
RV 10.121 (the Hiranyagarbha sukta) is another hymn dealing with creation, containing elements of monotheism. It has a recurring pada "what God shall we adore with our oblation?", in verse 1 named Hiranyagarbha "the golden egg", later a name of Brahma, in verse 10 addressed as Prajapati.
10.129 (the Nasadiya sukta) and 130 are creation hymns, probably the best known Rigvedic hymns in the west, especially 10.129.7:
- He, the first origin of this creation, whether he formed it all or did not form it, / Whose eye controls this world in highest heaven, he verily knows it, or perhaps he knows not. (Griffith)
These hymns exhibit a level of philosophical speculation very atypical of the Rigveda, which for the most part is occupied with ritualistic invocation.
- To those for whom the meath flows forth, even to those let him depart. (Griffith)
10.155 is against the "one-eyed limping hag" Arayi.
10.166, attributed to Anila, is a spell for the destruction of rivals, similar to 10.145, but this time to be uttered by men who want to be rid of male rivals.
10.173 and 174 are benedictions of a newly elected king.
The rishis of the 10th Mandala are divided into Shudrasuktas and Mahasuktas, that is, sages who have composed "small" vs. "great" hymns.
It cannot be a coincidence that both the words are composed by two different rishis with such strikingly similar, unusual and non-Indo-Aryan names. The rishi-ascriptions in book 10 are very often garbled. In the 2000 book “The Rigveda – A historical Analysis”, pp.25-26, Talageri had written: “Maṇḍala X is a very late Maṇḍala and stands out from the other nine Maṇḍalas in many respects. One of these is the general ambiguity in the ascriptions of the hymns to their composers. In respect of 44 hymns, and 2 other verses, it is virtually impossible to even identify the family of the composer“. It is clear that the composer of X.155 is the same as the composer of VIII.17, i.e. Irimbiṭhi Kāṇva.
Some verses in Book 10 (X.20.1; 121.10; 190.1-3) are found in the extant Rigveda, but missing in Śākalya’s padapāṭha. (Talageri 2008)
List of rivers and places
- Favour ye this my laud, O Gangā, Yamunā, O Sutudri, Paruṣṇī and Sarasvatī: With Asikni, Vitasta, O Marudvrdha, O Ārjīkīya with Susoma hear my call. First with Trstama thou art eager to flow forth, with Rasā, and Susartu, and with Svetya here, With Kubha; and with these, Sindhu and Mehatnu, thou seekest in thy course Krumu and Gomati.
- Rigveda X.75.5-6
Eastern regions in Book 10: 1. Iḷaspada-6, (nābhā-pṛthivyāh-6). 8. mahiṣa-1. 17. Sarasvatī-7-9. 28. mahiṣa-10. 30. Sarasvatī-12. 40. vāraṇa-4. 45. mahiṣa-3. 51. gaura-6. 53. Aśmanvatī-8. 60. mahiṣa-3. 64. Sarasvatī-9. 65. Sarasvatī-1,13, mahiṣa-8. 66. Sarasvatī-5, mahiṣa-10. 70. Iḷaspada-1. 75. Sarasvatī-5, Gangā-5, Yamunā-5. 91. Iḷaspada-1, Iḷāyāspada-4. 100. gaura-2. 106. mahiṣa-2, sṛṇi-6. 110. Sarasvatī-8. 123. mahiṣa-4. 128. mahiṣa-8. 131. Sarasvatī-5. 140. mahiṣa-6. 141. Sarasvatī-5. 184. Sarasvatī-2. 189. mahiṣa-2. 191. Iḷaspada-1
Western: Book 10: 10. (gandharva-4). 11. (gandharva-2). 27. meṣa-17. 28. varāha-4. 34. Mūjavat-1. 35. Śaryaṇāvat-2 64. Sarayu-9, Sindhu-9. 65. Sindhu-13. 66. Sindhu-11. 67. varāha-7. 75. Sindhu-1,3-4,6-9, Ārjīkīyā-5, Suṣomā-5, Gomatī-6, Mehatnū-6, Kubhā-6, Krumu-6, Śvetyā-6, Rasā-6, Susartū-6, Tṛṣṭāmā-6. 85. (gandharva-40-41). 86. varāha-4. 91. meṣa-14. 95. urā-3. 99. varāha-6. 106. meṣa-5. 108. Rasā-1,2. 121. Rasā-4. 123. (gandharva-4,7). 136. (gandharva-6). 139. (gandharva-4,6). 177. (gandharva-2).
Central rivers: 43. (sapta+sindhu-3). 67. (sapta+sindhu-12). 75. Vitastā-5, Marudvṛdhā -5, Asiknī-5, Paruṣṇī-5, Śutudrī-5.
Saramā-Paṇi myth in RV X.108
The Teutonic Vanir is connected with the Greek Hermes and Pan, but it is impossible to connect the two except through the Vedic Saramā and Pa ṇ i (see TALAGERI 2000:477-495 for details). 
The main Vedic myth which relates to the Saramā-Paṇi theme is found in the Rigveda in X.108, and it is found in later developed forms in the Jaiminīya Brāhmaṇa (II.440-442) and the Bṛhaddevatā (VIII 24-36). And it is found in both the Teutonic and Greek mythologies in versions which bear absolutely no similarities with each other, but which are both, individually, clearly recognizable as developments of the original Vedic myth. The myth, as it is found in X.108, incidentally, is itself an evolved and anthropomorphized form, located in the latest of the ten Books of the Rigveda, of an original nature-myth, found referred to at various places in earlier parts of the Rigveda, according to which ―Saramā is the Dawn who recovers the rays of the Sun that have been carried away by night‖ (Griffith‘s note to I.62.3) or by the Paṇis who are ―fiends of darkness‖ or ―demons who carry away and conceal the cows or rays of light‖ (Griffith‘s note to I.151.9). Talageri 2008