As we countdown the days to Infinity War, Thanos reigns supreme in the public eye.

After ten years of waiting, we will finally get to see him in a featured role in the Marvel Cinematic Universe after lurking mostly in the shadows throughout the films.

But what really drives the Mad Titan? From what we’ve seen from all the teasers and trailers, he comes to Earth in Infinity War to wipe out half of life on the planet in order to create balance. However, in the original storyline, his purpose was a bit darker. Not only did he succeed in eliminating half of all life on Earth, but with a snap of his fingers, he vanquished half of all life in the entire universe. And why did he do this? Not for balance, necessarily, but to win the favor of his plus one, Lady Death.

Whether it’s Thanos Quest or Infinity Gauntlet or the exceedingly popular Thanos Wins storyline, the Mad Titan always returns to the same point: he’s doing it for Death. Sure, he delights in the occasional genocide, but it’s all for nothing if he can’t have the love of his life by his side.

It’s unlikely that Death will be a character in Infinity War, and we can only wait and see if she appears in future films. However, her key issues will get a bump from Thanos’s surge in popularity as comic fans will always embrace Marvel’s power couple.

Lady Death made her first modern appearance in 1973’s Captain Marvel #26. This issue is showing signs of life, as it were, with the 90-day average for mid- to higher-grade CGC copies seeing a boost.

If you’re collecting Death keys, you have to aim for Thanos Quest and Infinity Gauntlet. Death is a major player in both those stories, and it’s in those comics that she comes into her own as a character rather than just the personification of, well, death.

In Thanos Quest, Death resurrects the Mad Titan in order for him to balance life and death in the universe. This is when he gazes into the Infinity Well and understands what the six infinity gems truly are. We know that Marvel is drawing from this idea of balance as Thanos’s motivation in Infinity War, so this would be the opening to bringing Lady Death into the MCU if they so choose. That also raises the collectibility of both Thanos Quest #1 and 2, which was already on the rise due to the Infinity Gauntlet making its first appearance in TQ #2. If Marvel decides to include her in the films, get ready for both those issues to skyrocket.

When piecing together your Lady Death run of key issues, you can’t leave out Infinity Gauntlet. This story follows Thanos Quest as he uses the gauntlet to not only eliminate half all life in the universe, but it helps him to become basically God when he traps the celestials and every other immortal, omnipotent being in the cosmos. However, it’s Death who helps bring about his downfall by continuously rejecting him, which sends Thanos over the emotional edge.

Not surprisingly, Infinity Gauntlet has become one of the hottest keys on the market. Virtually every grade of the 1991 Jim Starlin/George Perez classic is on the move. In some cases, it’s doubling in value from its 2016 average. Eventually, it will cool down, but if you are in the market to sell, now is the perfect time.