The evidence for Grey/Nordic/Reptilian alien encounters indicates these are beings in the physical, not extra-dimensional.

Fundamental for learning how to discern truth from fiction in ufology and the Alien Intervention is to imagine yourself a native person who encounters strangers on your shores. Realize that alien lives in the physical like you (but may be more adept in this encounter). See that any entity in the physical has the same needs as organisms on Earth–food, air, light, power: resources. Understand the more sophisticated in the mental environment, the more powerful. Maintaining a healthy skepticism about extra-dimensional realities might be a good idea.

The aliens encountered on Earth fall into a few types, including the Greys, Nordics, and Reptilians. Of those three, the Nordics communicate the greatest number of fallacies refuted by the Briefings from the Allies of Humanity, for example:

• “we are brothers”
• Earth as a “prison planet”
• “ascension”
• from another dimension

The Greater Darkness in the world today is hidden. It is deceptive. It portrays itself as benign and beneficial. It encourages people to acquiesce to its presence and to share in its mission here. It is not a spiritual force. It is a physical force. It is not comprised of multi-dimensional beings. It is comprised of physical beings from the Universe who present themselves in such a way that people will think the ‘visitors’ are mystical, spiritual and have magical powers. The only powers they have are their technology and their ability to convince you through persuasion in the mental environment.” –A Greater Darkness upon the World (April 11, 2001)

See this collection to judge the value of video evidence of Reptilians shape-shifting. They capitalize on exacerbating divisions among humans.

 The evidence for alien encounters on Earth is suppressed, distorted and denied.

The French government asserted in a 1999 study that United States government suppressed evidence of encounters with aliens.

People cannot speak of these things in public because it has been discouraged in the social discourse. That foreign craft are flying in your skies is an undeniable reality, and yet people do not want to think of it. – Preparing for the Greater Community (April 15, 2011)

The movie What the Bleep Do We Know? famously narrates a legend that the native Americans literally could not see Columbus’s ships, having no schema formed in their mind to accommodate their existence. This story has great truth in it, whether it represents eyewitness accounts or not. (Along the way to finding the “truthiness” quotient, a happy place to end up is to encounter Douglas Adams’ inhabitants of Kricket, with no concept of the sky “until a spaceship fell out of it.”) This does convey the magnitude of the threshold that the New Message from God describes as the greatest threshold humanity has ever experienced, its emergence into the Greater Community.

Humans encountering aliens are at a disadvantage in the mental environment. When the disadvantage is corrected, humans are greatly advantaged.

“Fools rush in where angels fear to tread.” Begin your investigation into the Grey/Nordic/Reptilian/Human encounter with all due respect for the unknown:

• with all due caution regarding power in the mental environment. See this  post, sent by a trusted source, an eye-witness narration of a demonstration of the power of mind over matter.
• with acknowledgement of the need for strength on the occasion of humanity’s entrance into a Greater Community of life in the universe.
• respecting the unknown affinity within yourself, the legacy of a connection to the Greater Community that you may bear like hidden treasure.
• regarding human development like naive adolescents in a big new city, like babes in the woods.

Greys, Nordics and Reptilians find humans unpredictable and undisciplined.

“[Races such as the Nordics, Greys and Reptilians] consider you brutish and self-destructive, and they seek to gain whatever they can from you before you destroy yourselves.”–Greater Community Spirituality, Chapter 11: What Is Your Preparation For?

They come seeking genetic material.

This footage portrays a Grey undergoing interrogation, with commentary from an contemporary eyewitness testifying to the authenticity of the footage from Area 51.

As Victor describes in the video above what he feels at liberty to say about his encounter with the Grey visitors, we see before our eyes one reason why they need our DNA. The Grey shows signs of growing suddenly feeble and overcome, demonstrating what the Allies of Humanity have said: Aliens find life on Earth an encounter with germs for which they have no immunity. They seek to hybridize their genes with ours so they can tolerate this life-abundant world.

“If any alien race tells you, ‘Well, we are here to enhance your genetic code,’ you must not believe this. It is not true. If you really want to be a laboratory animal, if you really want to be subjected to an occupation, if you think this is what it means to have contact with life in the Universe, then what is going to change your mind? Experiencing the occupation and waking up one day and saying, ‘My God! I am no longer a free person and I have no recourse’?”–The Allies of Humanity Book Two, Third Commentary: Understanding the Intervention

Aliens we now encounter on Earth come now with a distinct agenda that is different from visitors in antiquity.

Many thousands of years ago, in your time, several races came to interbreed with humanity to give humanity a greater intelligence and adaptability. This led to the rather sudden emergence of what we understand is called “Modern Man.” This has given you dominance and power in your world. This occurred long ago. However, the interbreeding program that is occurring now is not the same at all. It is being undertaken by a different set of beings and by different alliances.  —The Allies of Humanity Book One, Second Briefing: The Challenge to Human Freedom

Extraterrestrial races on Earth see our planet and our race as resources not to be depleted or destroyed but milked.

“Many people conclude that the visitors are beneficial because they haven’t already attacked us and taken over. What would you say to this?”
The Intervention is not here to attack humanity but to persuade humanity. The Intervention needs a compliant humanity to work for it and to engage with it to become part of its Collective. This assumption that humanity would be attacked and overtaken is entirely wrong. It is how you view gaining access to new lands and new resources.
But even in your modern world, economic, more than military, forces are used to gain acquisition to resources, and this is what is happening to the world regarding its relations in space. You are encountering small, economic Collectives who are here to begin the process of acquisition that larger nations can assume later on, if the Intervention is successful in establishing its presence and its power in your world.
To think that you would be attacked is wrong, and to think that because you have not been attacked that the forces that are here are beneficial is wrong. Both are based upon false assumptions. Therefore, the conclusions are incorrect.” —The Allies of Humanity Book Three, The Seventh Briefing: Questions & Answers