Gods of Blood and War
Several Gaulish gods are generally considered to have been universally worshipped throughout Celtic territories. Caesar also briefly mentions many of them, but instead of calling them by their Celtic names he falls back on the Roman habit of calling foreign gods by Roman names. Caesar refers to six of these gods, three of which he identifies as Jupiter, Mars, and Mercury.
Of the six, three are mentioned in the poet Lucan's epic Pharsalia, which describes Caesar's campaigns in Gaul. These are Taranis, Teutates, and Esus, whom Lucan describes as savage and cruel deities whose altars are soaked with blood. Lucan was probably using more than a little poetic license, but the gist of it was true.
Taranis is in all likelihood the Gaulish god whom Caesar equated with the Roman Jupiter in his writings on the Gallic Wars. The sole mention of Taranis by name in this context is by Lucan, who mentions him as one of three gods to whom human sacrifices were given. Lucan claims that victims were given to each god, killed in a manner appropriate for that god. Victims sacrificed to Taranis were reportedly burned, as would befit a god of lightning and fire. It is often speculated that the Wicker Man sacrifices described by Caesar might have been carried out under the auspices of Taranis.
Taranis is unmistakably a sky god. While he is often pictured riding across the heavens in a great chariot, he is less a god of the sun than a god of thunder. The main emblems of Taranis are his wheel, which he often holds aloft, and a thunderbolt. The name Taranis comes from a root meaning “thunder,” and he is closely related to the Norse god Thor. It was to Taranis that the collected heads of the slain were dedicated.
Esus, The Lord
The second of the bloodthirsty gods mentioned by Lucan was Esus or Hesus, whose name literally means “lord.” Little is known about this god, but the few remaining images of Esus depict him dressed as a woodsman, usually in the act of cutting down a willow tree. Sometimes, he appears to be emerging from the tree itself. Another emblem associated with Esus is the Tarvos Trigaranus, a bull accompanied by three cranes riding on its back, who appears to be a sacrificial figure associated with the willow tree.
Esus was closely connected to trees, and according to the same source, his victims were hung from trees and bled, with the direction of the runoff reportedly interpreted as an omen. This is evocative of rites to the Norse Odin, who may have originated as a Gaulish god. In the Norse Havamal, or sayings of Odin, a similar rite of sacrifice is mentioned, only with a twist — in order to gain the magical rune alphabet, Odin is sacrificed to himself.
Esus may also be connected to the legend of the Green Man, or forest spirit, the ever-present personification of the wildlands, or, in later tales, to the mysterious character called the “Man in the Tree,” or Derg Corra. Some have also speculated that there is a connection between Esus and Cuchulainn, the hero of the Tuatha Dé Danann. An episode wherein Cuchulainn fells a tree is often cited as evidence of a connection.
Strangely, Esus's appellation “Lord,” his self-sacrifice, and his iconic relation to trees caused both druids and Christians alike to associate him with Jesus, a rather strange comparison that continued to be made hundreds of years later. Even more strangely, images of Esus are often littered with nautical symbols — anchors, sea birds, and so on — and one of the best-preserved monuments in his honor was erected by ancient sailors in France, called the Pilier des Nautes, “Pillar of the Sailors.” Commenters on the Pharsalia have equated Esus with both Mercury and Mars.