Father Luis Gomez is an antagonist in The Amber Spyglass the third book of His Dark Materials trilogy. Father Gomez is the assassin the Church send to kill Lyra Belacqua because she is Eve incarnated and in their view she will doom humanity to darkness again. Father Gomez is so eager to kill Lyra, because he is a fanatical young priest who has flagellated himself all through his life, eager to see God and reach Heaven, and he is willing to set out on a seemingly suicidal mission because he believes he is saving the world.
Despite being an assassin, Father Luis is a very affable man and charming and polite even with his minions and enemies. Father Luis is the youngest member of the Consistorial Court of Discipline; he is a devoted cardinal and he is in one of the highest organizations the Church has. Father Luis has a dark side, though as he is willing to kill a twelve year old girl simply to save humanity.
Father Luis cares more about humanity than the world, or even the Multiverse itself - he doesn't know Lyra is the only being holding existence together, and that if he killed her all would end, and even if he knew this, chances are he would kill her anyway.
Father Luis has an odd view of good and evil; upon seeing Lyra before he aims to kill her ("He couldn't understand how anyone so deeply immersed in evil could be so happy.") Father Luis is suggested by Father McPhail, his master, not to follow Lyra, but to follow Mary Malone, the scientist from Oxford, who has also entered another universe. Father Luis is told that if he follows Malone, she will bring him to Lyra. This he does, but is way behind her, because when she is in the world of the mulefa (elephantine creatures with wheeled hooves) Father Luis is a world behind her, in Cittagaze.
At last, Father Luis enters the mulefa's world, despises the mulefa on sight, and makes a deal with their enemies, the tulapi swans, which Father Luis organizes to attack the mulefa and eat their possessions. Father Luis causes chaos in the mulefa town and he eventually sees Lyra, and aims at her, having her right in his gun sights. Just as he is about to shoot however, his daemon is grabbed by the angel Balthamos, who struggles with Father Luis. Luis realizes who his attacker is when he feels his feathery wings, and he says "Shouldn't we be on the same side?" Balthamos says he won't side with an assassin and he holds the priest's head deep underwater and eventually his daemon disintegrates. Father Luis is dead and his corpse nourishes some lizards who come out scavenging later.