Elfric is an antagonist of the fantasy comic series Sláine by Pat Mills. He first appeared in the story Time Killer (2000 AD progs 411-434, 1985) as "Elfric Serpent-Eye", the changeling leader of a force of Norsemen in the Battle of Clontarf. Sláine's sponsor, Myrddin, gave Sláine the task of killing Elfric, explaining that Elfric was an agent of the Cythrons, a pre-human race of aliens who sought to alter the course of history by fomenting wars and farming humans like swine.
Elfric is not himself a Cythron. Rather, he is a Dark El (colloquially known as 'Dev-Els', in contrast to the Light Els or 'Ang-Els'); a native of the El worlds (which he calls 'Els-Where'), which are located on dimensions at right angles to our own. These realms are analogous to the Fairy realms, and as such Elfric exhibits many traits common to these creatures of legend, including immortality; immunity to pain and injury; and a loathing of iron. He bears only a passing resemblance to humans, and is usually depicted with blue skin, needle-shaped teeth, and his most distinctive feature: a third eye set in the middle of his forehead, from which he is able to project bursts of deadly energy. He has also on occasions exhibited a talent for shape-shifting, though he usually has to take pains to hide his third eye, making his disguises imperfect. He favours heavy make-up, and often has a mocking, sadistic manner matched by an appetite for debauchery and decadence.
A skilled and sadistic warrior and sorcerer, Sláine was only able to defeat him in battle by using his warp spasm, and even then was still mortally wounded: an event he only survived by way of the temporal manipulations of Myrddin and the Ever-Living Ones.
Elfric too survived the battle, but was banished to Els-Where, where he met Sláine and his new ally Murdach, and he was killed in battle once again. His immortality once again preserved him, but under the 'laws of the macrocosm' he felt certain that he could not be defeated a third time. He did not have long to wait for this third conflict. Later, in the realm of Cythrawl (really pre-historic Earth), Sláine orchestrated a revolt amongst the Cythrons' human gladiators. The Cythrons were about to put this revolt down, forcing Myrddin to intervene directly by summoning elementals. This direct intervention allowed Elfric to appear to confront his bitter enemy, and sure enough, Sláine was unable to harm him. Following advice from his goddess, Sláine at least proved capable of matching Elfric, and thus became 'immune' to him.