Abel הבל
Adam's second son, a shepherd, the first victim of murder
The name Hevel means «vapour» or «breath» — the same word Kohelet opens with. His life is short and the Torah says almost nothing about him except that he was a shepherd and brought «from the firstborn of his flock and from their fat»: explicitly the best, unlike his brother's offering.
His gift is accepted, and for that he is killed in the field. God tells Kayin, «the voice of your brother's bloods cries out to Me» — in the plural. The sages explain: his blood and the blood of all the descendants who will now never exist. From this comes the Mishnah's famous rule that one who destroys a single soul destroys a world, and one who saves a single soul saves a world.
Hevel left no children and no line; Shet took his place. Tradition remembers him as the first righteous man and the first martyr.