So, I've been doing a lot of poking around online about the obelisk from Agents of Shield, and the common thought seems to be that this houses either a Terrigen Crystal or the Terrigen Mists. While I agree with this theory, the issue that I have come across is that there doesn't appear to be a lot of discussion as to why, and so in this article I will attempt to answer this question using my knowledge of Marvel Comics. In addition, due to the obscure nature of the Kree, the Inhumans and the Terrigen Mists to all but the most avid of Marvel Comics readers, I thought the first and best thing to do would be to explain each of these.
1. The Kree - We can all say with relative certainty that the alien in the season 1 episode Tahiti was a Kree. This is further evidenced by the fact that Marvel has brought the Kree into the Marvel Cinematic Universe with Guardians of The Galaxy. For those of who unfamiliar with the Kree, these are a race of aliens whose infancy predates humanity by millenia. The Kree physiology is such that they are several times stronger and more resistant to injury than a normal Human.
2. The Inhumans - At some point the Kree had visited Earth and experimented on primitive Humans which led to the formation of the Inhumans. Inhumans are exactly like normal Humans until they are exposed to the Terrigent Mists. Once this happens, the dormant Inhuman gene within them "activates" and they gain abilities. Sometimes these abilities are as basic as enhanced strength but can also be extreme as in the case of Black Bolt, the King of the Inhumans, whose voice emanates a sonic scream capable of destroying entire planets.
3. The Terrigen Mists - The Terrigen Mists are exactly that, mists. An Inhuman undergoing exposure to the Terrigen Mists is a process called Terrigenesis. During this process, the Inhumans in question is engulfed in the Terrigen Mists in the same way that you would engulf yourself with steam in a sauna. The result is that again, their dormant Inhuman gene is activated. This is best compared to when chromosomes organize themselves into a fetus becoming a man or a woman.
Moving on, in Season One of [Agents of S.H.I.E.L.D.](series:722469), we learned that the blood of a Kree was used to bring Agent Coulson back from the dead. This is is particularly important here because this is not the first time we have seen this happen. In Marvel Comics, this had taken place with a heroine named Carol Danvers, more popularly known as Ms. Marvel. In the Marvel Comics, the origins of Carol Danvers' powers were revealed to have been due to a blood transfusion by Captain Marvel. What we are seeing over the course of Agents of Shield Season Two appears to be exactly what we saw with Carol Danvers in Marvel Comics: Agent Coulson is slowly taking on the attributes and physiology of a Kree. This is one of the reasons so many of us in the Marvel Comics community believe Phil Coulson may go on to become Captain Marvel who was, in the comics, a member of the Kree empire.
Now because Marvel has gone to such lengths to lay this foundation of the Kree in Agents of Shield and in the films, it stands to reason that we will see some kind of Inhuman element in the Marvel Cinematic Universe and this is doubly so as Marvel Studios has stated that they want to make a film based on the Inhumans. The question now is how they would go about introducing the Inhumans. Traditionally, Marvel has relied on post credit teasers to inform us of coming characters and projects but because origins will no longer be a part of the Marvel Cinematic Universe, we are left with the introduction of various characters in Agents of Shield to provide the backstory that would normally be reserved for their respective films. It is my belief that Marvel is going to use the obelisk as a way to segue into the Inhumans by revealing that this obelisk is an object discovered prior to World War II and captured by Agent Carter and The Howling Commandos. I take this opinion because it seems clear due to how the items is handled in Season Two Episode One, that Agent Carter and her forces are aware of what the obelisk is capable of, even if only on a basic level. The problem here is that Marvel is getting into territory unexplained in the early Inhumans stories and even now, is only explained by context.
Since we know how the Terrigen Mists react to Humans with an Inhumans gene, the next step would be to ask what would happen if the Terrigen Mists were exposed to a Human without the Inhuman gene. Again, to the best of my knowledge this is only explained with context and we're not given a definitive answer by Marvel. In the fallout of a recent Marvel event called 'Infinity' where by Thanos sought to eliminate his offspring from the cosmos, the Terrigen Mists were spread throughout the world and everyone on Earth with an Inhuman gene had that gene activated which led to the Inhumanity event. What we did not see during Inhumanity, were the grotesque effects and eventual death of normal Humans who touched the obelisk as we had seen in Agents of Shield. What we do see however, is that Raina is able to touch the obelisk without succumbing to its effects. Furthermore, the obelisk seemed to react to her physical touch indicating that she may have passed the 'genetic test', but again, we do not see any kind of physiological change which is synonymous with Terrigenesis.
Regardless, this is entirely speculative and the obelisk may simply be an object created specifically for the Marvel Cinematic Universe rather than an existing object from the Marvel Comics, or it could be a variation of the Terrigen Crystals. Either way, I am excited to see how this story unfolds in Agents of Shield.