Vellioth, also known as 'Vellioth "the Martinet"' was a vampire lord in Baldur's gate 3 who succeeded Donella Szarr and was later murdered by his underling Cazador Szarr.
His appearance in fan art is "headcanon" (not official) as he is only seen as a skull after his death in the game. The most popular design shows him as looking similar to Astarion with long and curly white hair and the typical red vampire eyes. Most art portrays him as a drow or a high elf.