He is non-canonical as he never appears in the books.
During the War of the Ring, which resulted the time when the One Ring had awoken and was willing to return to the Dark Lord Sauron, Elviondel was among the elves that refused to leave Middle-earth and prefered to fight against the enemies of Mordor and Isengard. Deciding to protect the country of Rohan, Elviondel accompanied Haldir to the old fortress of Helm's Deep and aid the Rohirrim and their king defending the fortress from an army of 10,000 Uruk-hai that were bred for war, and were tasked by their master Saruman to slaughter the Rohan's people. Hoping to protect the innocent mortals, Elviondel was stationed at the Deeping Wall like every elf. It is unknown if he survived the battle, but since his death was never shown, it is most likely that he was one of the fewer elf survivors that returned to Lothlórien and live throughout the Fourth Age after the One Ring was destroyed, resulting the death of Sauron.
- The Two Towers (film) (First appearance)