Some stories can really only happen in comics. While many of us know and love the X-Men, a big part of their appeal is their sprawling, often utterly nonsensical continuity. While we all know Superman, only through the comics could we have witnessed a love story between him and Lois Lane change and grow over 80 years to become an iconic, culture-shifting story. And only in comics would we be introduced to a character like Thanos, a planet-hopping interdimensional tyrant who commits genocidal crimes with the sole purpose of pleasing and winning the affections of the literal Grim Reaper.
In Marvel, Death usually appears in the form of a cute goth lady who wears either a black dress or a dark gray robe. Her character traits are somewhat limited, as she's often shown quietly surveying the actions of others. Thanos, on the other hand, is loud, boisterous, and prone to extensive monologues. A Jim Starlin creation, his character design is a mix of inspirations from Jack Kirby's Fourth World characters, particularly Metron and Darkseid. Like Darkseid, Thanos is a fascist and a murderer. Unlike Darkseid, Thanos has a weakness in his on-again, off-again girlfriend, Death.
Thanos was born on Titan, one of the moons of Saturn. His parents were Eternals, a breed of superpowered immortals. It's usually best not to ask too many questions about the Eternals, because it doesn't make a lot of sense, and their story is pretty classist. To wit, their “cousin race” is essentially known as the Deviants, because they are deformed while the Eternals are physically perfect. In this story, beauty = morality, so the Eternals are good while the Deviants are bad. There's a bit more to the story, but to understand Thanos, you have to understand that he was born to Eternals while he himself had features of a Deviant. An inability to accept his mutation caused his mother to immediately attempt to murder him.
Thanos is a jerk, but it's kind of understandable. He didn't have a great start in this life, and it doesn't get much better. Initially a pacifist and kind of a nerd, Thanos grew up very shy. He met some friends, only to watch them be devoured by lizards. No joke, that actually happened in a comic. His pacifism comes to an abrupt end, and he, in turn, kills the lizards. Fortunately for Thanos and unfortunately for everyone else, he's finally found something he likes to do, so he goes on a murder spree, killing several classmates. In Thanos Rising, it is assumed that Thanos tortured his mother to death.
Most stories about Thanos focus on him being betrayed by his mother, ultimately professing that all he really wants is to be loved. Often, the women in Thanos' life are the scapegoats on which his genocidal tendencies lie. Through his earlier exploits, Thanos fatefully catches a glimpse of Death, and this match-up between a conceptual entity and a genocidal maniac is love at first sight. Thanos falls deep for Death, killing all of his children and all of the crew on his ship. He returns to Titan and bombs it from afar, killing most of its inhabitants. When that does nothing to catch Death's eye, he moves on to the rest of the universe. This brings us to Infinity Gauntlet, a now-classic tale in which Thanos kills half of the universe as sort of a Valentine's Day card to Death. Thankfully, although he succeeds, the horror is ultimately undone, and he is rejected by Death once more.
In the comics, Death doesn't often speak, only communicating verbally when it suits her. She is an expert manipulator, toying with Thanos by occasionally expressing interest in him, then either outright vanishing or accusing him of a terrible betrayal and demanding a greater sacrifice for her suffering. Thanos' betrayal, according to Death, is that he insists on being her better rather than just her equal. In Thanos Quest, he travels the universe, murdering each person in possession of an Infinity Gem, gathering them all and presenting them to Death. Very much like the lyrics of a Misfits song, Death gives him a throne at her side. However, she still refuses to speak directly to him, using an ill-fated rat-human hybrid to deliver her responses. This infuriates Thanos, who rips her messenger to shreds and storms out. For her part, Death sits contentedly alone, while Thanos chastises himself for being “foolish” and miscalculating his move to win her heart. Understanding that he failed, Thanos takes to the stars, determined to try again.
A spurned Thanos tries to make Death jealous by creating Terraxia, a woman who looks and acts almost exactly like Thanos. This gives us a look a little too far into Thanos' narcissism, as he declares Terraxia to be “everything that you're not!” to a mildly amused Death. Terraxia isn't long for this world, though. She manages to commit a few brutal murders, then gets transported to deep space, where she dies due to lack of oxygen.
Bizarrely, Deadpool has a role in this story, too. While he was teetering between life and death in his days at Weapon X, the specter of Death would appear to stand over him, keeping watch. Deadpool's a little bit troubled, to put it mildly, and feels himself falling for the skeletal apparition that haunted his days. Death seems to reciprocate his feelings—although, of course, it's difficult to know how genuine that is on her part. After a very strange courtship, an enraged Thanos intervenes. Seeing that Deadpool wishes for death, Thanos curses him to immortal life. In the Deadpool vs. Thanos series, Deadpool realizes that Death has been toying with him and Thanos both, and ultimately decides that he worships life in all its chaos much more than he worships death, accusing Thanos of the same. An infuriated Thanos attempts to destroy Deadpool, then goes crawling after Death once more.
One of the strangest parts of a very strange story is the entity created by Thanos and Death called The Rot. Thanos dies, and his death causes the birth of a sort of love child between him and Death. Although the entity is difficult to describe, it's essentially a negative presence floating around in space, so even Death herself doesn't notice birthing it. (“Birthing” might not even be the correct term, but The Rot is very loosely defined.) The Rot isn't just an entity, either, but a place the Avengers actually enter to battle Thanos. Ultimately, Death and Thanos team up to destroy The Rot, which is causing them more problems than it appears to be worth.
In the most recent of Thanos' ongoing series, we discover he has taken ill and become vulnerable. Even a slight weakness presents an opportunity to see him destroyed. Very few relatives of Thanos survive, but the ones that do come after him, including Starfox. Many characters wish to rid the universe of “The Mad Titan” and put together a ramshackle band of misfits to complete the task. Thanos' long-suffering son, Thane, appears at the side of a pale, dark-haired woman, who appears to be pulling his strings. This woman, of course, is Death, although she is a Death who has foregone her skeletal form for a more Suicide Girls-inspired look in this incarnation. She convinces Thane to destroy his father and leave him powerless, wandering the universe as a beggar. When he does, she manipulates Thane into committing a constant series of murders, declaring open war and bringing her thousands of souls. Thanos comes back to confront his son, who he had abandoned early on, while Death smirks at him from Thane's side, baiting them to continue their fight.
One of the most interesting things about Thanos is that, for all his power, for all the atrocities he's caused, for all the lives he's taken, and for all his extensive monologues, he's still, at heart, just a rejected child, craving the attention of a woman who won't give him the time of day. As awful as he is, the reader gets a sense of satisfaction watching him get repeatedly rejected by the one thing in all the cosmos he appears to actually care for.
Death, on the other hand, in comics as in real life, remains a mystery.