“Fine, I’ll do it myself,” growled Thanos in a mid-credits scene after Avengers: Age of Ultron. All around the world, fans heard a collective "SPLOOSH!" as their Captain America briefs were simultaneously ruined. In that scene, the MCU’s Big Bad donned the Infinity Gauntlet, the golden glove which becomes the most powerful weapon in the universe when all six Soul Gems are collected — wait. What’s a Soul Gem?
The objects the Marvel Cinematic Universe refers to as the "Infinity Stones" were originally called "Soul Gems" in the comics, though they are now known as Infinity Gems on the printed page. According to The Collector (Benicio Del Toro) in the MCU, the Infinity Stones were created during the Big Bang, remnants of six original singularities. In the comic books, the Soul Gems were once a primordial being known as Nemesis, who ended its existence because it was lonely being the only sentient being in the universe.
So what are Infinity Stones? Regardless of which cosmic canonical origin you prescribe to, the Stones are the Stones, and the MCU has introduced five of the six. The six stones each represent one aspect of the universe: Mind, Power, Time, Space, Reality, and Soul. Whoever holds a stone has total and universal control over its corresponding aspect. Long story short, it’s probably not ideal that a guy nicknamed the “Mad Titan” is trying to collect them.
While the Infinity Stones of the MCU are essentially the same as the Infinity Gems of the source material, there are notable differences beyond the flip-flopping and swip-swapping of colors. So, let’s untangle this knot and figure out the differences between the Soul Gems and the Infinity Stones.
Soul StonePhoto: Marvel Comics
Ironically, since it was the last Stone to make an appearance in the MCU, the Soul Gem was the first Stone introduced in the comics in Marvel Premiere #1 (1972). The most interesting thing about the Soul Gem is that it is sentient. It actively hungers for souls and can steal and control them (living or dead). It also allows the wielder to steal the powers or abilities of their victims.
In the comics, the Soul Stone has a pocket universe within it known as Soul World, an idyllic and peaceful paradise in which the original keeper of the Stone, Adam Warlock, would trap rowdy folks, and occasionally enter himself. Well, technically the High Evolutionary was the first keeper of the Stone, but he gave it to Adam Warlock for protection. We can’t yet say what the powers of the Soul Stone will be in the MCU, but we at least know that it will differ in color. In the books the Soul Stone is green, which obviously it can't be in the movies as the Time Stone already claimed that color. If the MCU follows the color conventions of the original Gems, the Soul Stone will be orange.
Time StonePhoto: Marvel Studios
The Time Stone shows up in Doctor Strange, and beyond the change in color, it pretty perfectly displays the Gem's abilities in the books. In Doctor Strange, it is green and contained in an amulet called the Eye of Agamotto, which the Sorcerer Supreme used to thwart Kaecilius and Dormammu.
In the source material, the Time Gem is orange. It affords "the user total control over the past, present, and future." It can manipulate time in every possible way: stop it, slow it down, speed it up, reverse it, and pretty much anything else you can think of. It allows time travel and the ability to alter the past or future. And, as Benedict Cucumberpatch displayed in his fight against Dormammu, it can trap beings in unending loops of time. At its full power alongside the other gems, the Time Gem grants omniscience: knowledge of all things in existence at once. Its first comic book appearance is alongside the Power Gem in Marvel Team-Up #55 (1977).