“Pye-roon”, Russian: Перун
Perun is one of the most important gods in Slavic paganism, both mythically and in practice. He is described as “a great and vigorous man, red bearded, with an axe or hammer in his hand that he threw at wicked spirits” . Perun was worshipped by all the pagan Slavs, but stood proudly among the Kievan Rus.
Perun is first and foremost a god of thunder. “The Greek historian Procopius writes as follows concerning the Slavs at Antae: ‘They believe that there is one single god who is the creator of the lightning and the sole lord of all things, and to him they sacrifice cattle and all sorts of animals…’” . While Perun undoubtedly an incredibly powerful god, we should not simply take Procopius’ word for it that Perun was in fact a ‘creator’ or the primary figure in the pantheon. Instead, let us look to further historical, folkloric and linguistic evidence.
The Indo-European root of his name, *per-, meaning “to strike”, is also seen in other Indo-European thunder gods: Baltic Perkunas, and Vedic Parjanya . The “striking” function of Perun can be seen through these related counterparts.
Parjanya shares a great deal with Perun in both qualities and actions. “[Parjanya] shatters the trees, and shatters the devils; the whole world fears him of the mighty weapon. Even the innocent man hurries away from him of manly strength, when Parjanya, thundering, smites the evil-doers”  Smiting “evil-doers” or, more specifically, oath-breakers recurs throughout the treaties signed by the Rus in the Russian Primary Chronicle:
“According to the religion of the Russes, the latter swore by their weapons and by their god Perun, as well as by Volos, the god of cattle, and thus confirmed the treaty”; “If any of these transgressors be not baptized, may they receive help neither from God nor from Perun: and may they not be protected by their own shields, but may they rather be slain by their own swords, laid low by their own arrows or by any of their own weapons, and may they be in bondage forever,”; “In the morning, Igor summoned the envoys, and went to a hill on which there was a statue of Perun. The Russes laid down their weapons, their shields, and their gold ornaments, and Igor and his people took oath (at least, such as they were pagans), while the Christian Russes took oath in the church of St. Elias…” 
While obviously the function of the Thunderer as oath keeper is shared between the two, the uniquely Slavic element of this mythic association is the recurring curse placed on those who violate oaths: may their own weapons kill them. Further, seeing that the Rus “swore by their weapons”, Perun’s connection with weaponry is historically clouded but significant. This is apparent even if the Russes “laid down their weapons” before swearing the oath in front of the idol, a sacred space. Helmond echoes this aversion to weaponry surrounding the sacred space when describing the sacred oaks in Oldenburg, saying that “…the Slavs show such reverence for their holy things that they do not allow the neighborhood of a fane to be defiled by blood even in time of war” . He also states Slavs were reluctant to ever swear an oath, fearing the “avenging wrath of the gods” . Although he does not name any gods particularly, considering this is mentioned in a passage describing the sanctuary of Prove, and compared with the Primary Chronicle, it is safe to interpret this as fear of Perun.
Perkunas, being of Baltic origin, is more closely connected to Perun than Parjanya, being within the same language family. He was prayed to and given offerings during thunderstorms for protection . Further,
“[w]hen [Perkunas] smites a devil with his bolt, he does not kill the fiend, but merely strikes him down to hell for seven years, after which the demon again appears on earth, just as Indra[, related to Parjanya,] and his Iranian doublets (especially Thraetaona) do not slay their antagonist, the storm-dragon, but only wound him or imprison him so insecurely that he escapes, so that the unending battle must be constantly renewed” .
Similarly, one of the Thunderer’s most significant mythological functions is his ceaseless battle with the Serpent of Death on Earth. Looking at Perkunas, we can say that Perun’s conflict with Veles also does not simply happen once but continues throughout mythic time eternally.
Perun’s analogous Christian saint St. Iliya/Elias is called “Gromovnik”, meaning “thunderer”, in Serbian traditions . His name was used to translate “Zeus” into old Bulgarian, and he is described as an “angel of thunder” alongside Khors in Dialogue of the Three Saints . These two names being listed alongside one another is theologically significant but must be understood through comparisons with other closely related mythologies.
Looking at Vedic hymns, we see that Agni, the god of fire, is identified as Indra . In a later hymn, Indra is acknowledged as the same as Parjanya . Through these two hymns, the rain god Parjanya, the war god Indra and the fire god Agni are all said to be the same deity. A unity between Parjanya, Indra and Agni is made between these two hymns. Turning to Lithuanian folk songs, we observe that Perkunas plays a part in the marriage of the ‘Morning Star’, “and it is possible that all his association with dawn or sunset is secondary and due to the likeness of evening and morning glow to the lightning’s fire…”  In these related religions, lightning and fire were seen as fundamentally related, both in a profane and a mythological sense.
Khors and Perun appearing side by side in this apocryphal text now appears more significant than simply listing names. Perkunas and Indra/Parjanya, seen either as related to or the same as gods of fire and the sun, play the same roles in their respective mythologies as Perun does within Slavic myth. Looking at these closely related mythologies, we can speculate about the relations between Khors-Dazhbog and Perun.
While we don’t have enough information to say that Khors and Perun are the same god (and, in fact, historical sources and etymology point to them being distinct), their relation cannot be denied. Insofar that Khors-Dazhbog is a son of Svarog, it would make sense to say Perun is his brother. This is because Perun was likely the Zuarasicz/Svarozic worshiped at Rethra, based on description of the idol  when compared with the idol of Perun at Kiev in the Russian Primary Chronicle . It is significant that both describe the metal elements of this otherwise wood idol, something which does not occur with depictions of idols of gods other than Perun throughout the chronicles.
But the ties between Perun and Khors-Dazhbog do not stop there. Their mythological associations overlap to a certain extent.
Perun is certainly associated with rain. The Serbians venerating St. Iliya Gromovnik “pray to him as the dispenser of good harvests” . Similarly, in the Baltic, “[Perkunas] controls the rain and thus the fertility of the fields. In the life of the peasants, Perkunas plays the most important role, and it is he who is offered sacrifices on the occasion of droughts and epidemics” . The Rig Veda states that “From afar roars (as) of a lion arise, when Parjanya makes the rainy mass of clouds. / The winds blow forth, lightning-flashes fall, plants shoot up, the heavenly light-space overflows. Refreshment is produced for the whole world when Parjanya favours the earth with his seed” .
However, Dazhbog’s name is etymologically connected to dat’ “to give” and dozhd’ “rain”. Further, the sexual imagery of the Hymn to Parjanya is echoed in the etymology of Khors’ name, related to Sanskrit hṛṣu . Etymological evidence also suggests that Khors-Dazhbog may in fact be the same figure as Yarilo, the fertility god associated with the yearly coming of spring (his name related to German “Jahr”, English “Year”). There is no direct explanation for these similarities, but we must account for them when worshiping the gods.
While in a profane sense, they can simply be explained as “the likeness of evening and morning glow to the lightning’s fire” , the importance of these similarities to the sacred in Slavic reconstruction cannot be ignored. It becomes clear then that a dual hierophany occurs when lighting a candle on an altar: both Khors-Dazhbog and Perun are made present, both the heavenly gods make the space sacred. This echoes Vedic traditions of a fire altar making a sacred space . In this sense, both are ‘giving gods’. The difference between the two being that Khors-Dazhbog remains a rain god and fertility-giver, while Perun extends his ‘giving’ to punishment for oath-breaking.
Besides lightning or rain, a third theophany of Perun is the oak tree . He shares this feature with other Indo-European thunder gods; look to Donar’s Oak among the Saxons or Zeus’s Oak in the Iliad. The oak was in fact so sacred that among the Elbe Slavs, an oak grove consecrated to “Prove”, commonly accepted to be a corruption of Perun , was forbidden to all except priests, those making sacrifices, and those seeking asylum .
While statues of Perun stood in Novgorod and in Kiev, and as Svarozic in Rethra, the sanctuary of Prove at Oldenburg is described as without idols . Similarly, the worship of Perkunas during thunderstorms does not mention any statues present before the worshipper. The idol of Perun can then be understood as a fourth theophany. Perun is present in lightning and thunder, in rain, and in the oak, but “[w]hen no sign manifests itself, it is provoked,” . However, even this was done in fear and in piety, without weapons and cognizant of the Thunderer’s incredible power, as we see in Baltic prayers to Perkunas  and the Hymn to Parjanya .
Solntsa Roshcha Interpretation
Perun is the son of Svarog (Svarozic) and brother of Khors-Dazhbog. They represent the gods of the heavens, given powers directly from their father. Perun is in eternal mythic conflict with Veles, and the two should not be invoked together or given offerings in the same ritual. Worship of both can be maintained and is historically attested. They simply should remain separate, out of respect.
Perun may be invoked and given offering in return for making a space sacred. His axe drives away spirits and consecrates a space for the gods. Both he and Khors-Dazhbog possess this power. Invoking Perun is highly advisable when consecrating an altar or grove, with the exception of the worship of Veles.
Iconography of weapons, thunderstorms, lightning, rain or oak can all be used to make Perun present at an altar. However, especially avoid bringing weapons within or near a place consecrated to Perun.
Perun should be invoked and offered to when swearing oaths. A variation of “Perun, let my own words/weapons strike me down” would be an adequate reconstruction based on the Russian Primary Chronicle. The exception again being an oath sworn to Veles. Offerings to Perun may themselves be oaths. These offerings would be especially valued by Perun.
Perun is most present during a thunderstorm, when he engulfs the heavens. At the same time, he is most dangerous during a storm. Consider praying to him for protection. Similarly, he is most present on Kupala Night, the Summer Solstice, the peak of his season as Thunderer.
Prayer for Consecration of a Sacred Space
(Incense and/or Candles necessary; iconography optional)
Invocation: Thunderer, Great Oak, Hero of the Heavens, First at Kiev, First at Oldenburg, come to me. Son of Svarog, Serpent-Striker, Sun’s Brother, do not strike me down, but hear my prayer.
Petition: By your axe I swear, Perun, that I come to you out of respect and in peace. If I harbor any ill intentions, let the gods turn their back on me and let my own words turn against me.
Offering: By your Axe and Thunder, by your Oak and Lightning, by you, Perun, I swear to honor the gods and my ancestors. I offer to you this space for that purpose. With you axe, drive away foul spirits. With your Thunder, throw out the profane. With a great oak, let its sacred roots grow. With lightning, keep my hearth fires flaming forever.
Slava Perunu, shtormov bog!
 “The Deities of the Elbe Slavs.” Mythology of All Races, Volume 3: Celtic and Slavic. Jan Machal. Cooper Square Publishers, 1964. Pp 277-78
 “Perun.” Mythology of All Races, Volume 3: Celtic and Slavic. Jan Machal. Cooper Square Publishers, 1964. Pp. 293-296
 “You, O Agni (Fire), are Indra, the bull (strongest) of all that exist;” “Rig Veda 2.1.3.” The Beginnings of Indian Philosophy. Translated by Franklin Edgerton. Harvard University Press, 1965.
 “O Maruts, grant us the rain of heaven; make abound the streams of the lusty stallion.” “Rig Veda 5.83.6.” ibid; Edgerton notes that the “lusty stallion” refers to Parjanya and that the Maruts, “regularly followers of Indra”, are here presented as followers of Parjanya, implying the two figures to be one and the same deity.
 “Baltic Mythology.” Mythology of All Races, Volume 3: Celtic and Slavic. Louis Herbert Gray. Cooper Square Publishers, 1964. Pp. 321-22
 “Non-Iranian Origin of the Eastern-Slavonic God Xursu/Xors”, Constantine L. Borissoff. Studia Mythologica Slavica, 2014. pp. 17
 “Their town is very widely known as Rethra, a seat of idolatry, where a great temple had been erected to the demons, the chief of whom is called Redigast. His image is ornamented with gold, and his bed decked with purple.” Chronicle of the Slavs. Helmond. Translated by Francis Joseph Tschan. Columbia University Press, 1935. Pp. 50; It is important to note that it is widely accepted that the name of this god was not in fact “Redigast” and that this is in fact a mistake on the chroniclers’ part, who confused the name of the fort with the name of the god. Secondly, Tschan writes in a footnote that Thietmar described the very same idol as “wood, adorned with gold and carved with inscriptions”, which sounds even more like Perun at Kiev.
 Russian Primary Chronicle. Translated by Samuel Hazzard Cross. Edited by Olgerd P. Sherbowizt-Wetzor. The Medieval Academy of America, 1953. Pp. 64, 74, 77
 “Vladimir began to reign alone in Kiev, and he set up idols on the hills outside the castle with the hall: one of Perun, made of wood with a head of silver and a mustache of gold…”; ibid, pp. 93
 “Rig Veda 5.83.2-4.” The Beginnings of Indian Philosophy. Translated by Franklin Edgerton. Harvard University Press, 1965.
 “Slavic Paganism.” A History of Religious Ideas, Volume III. Mircea Eliade. Translated by Alf Hiltebeitel and Diane Apostolos-Cappadona. The University of Chicago Press, 1985. Pp. 29-33
 “Religion of the Balts.” Ibid, 25-29
 Chronicle of the Slavs. Helmond. Translated by Francis Joseph Tschan. Columbia University Press, 1935. Pp. 218-219
 The Sacred and the Profane. Mircea Eliade. Translated by Willard R. Trask. Harper & Row, 1959. pp. 30
 ibid, pp. 27