The following is a video transcript

Todd Kenreck: There are a few very iconic monsters in the D&D multiverse, but the eidolon, and the Scared Statue, have the very unique place in the D&D multiverse.

Adam Lee: The pictures in Mordenkainen's is of Moloch, a statue of Moloch which appears on the player's handbook, the first edition player's handbook. The whole thing about eidolons is that they're these spirits that come from ... Whether they were human or what, a human-type of character. It could have been an elf or a dwarf or anything. But these spirits that were dedicated to a certain god or a certain sacred site in their life, upon their death, the god creates them into these eidolons, these spirits that can inhabit a statue and bring it to life and act as a guardian of an area.

If I was a follower of Lathander, I could be a devout stalwart paladin guarding this area, I die, and upon my death Lathander turns me into an eidolon and then I can inhabit this sort of temple and I can be its guardian for eternity. And if anybody comes and defiles it, my spirit can then inhabit a statue and bring it to life and then I can kind of defend it or speak through the statue and defend its sanctity.
However, evil things can also be created from eidolons. So you can have a dark priest of Moloch in this case, and that priest could be then sacrificed on an altar and the spirit rose and then been bound to this area and said now you're gonna defend this site. And an eidolon can inhabit any kind of statue or any kind of object that's humanoid shaped. They can then animate it and speak through it.
So eidolons can be good, they can be evil, and they can be neutral. It doesn't matter. But they are guardians.
And I always thought it would be fun as a DM to ... If a character died in one of my adventures, then I could ... If that was it, they were done for, to have the god resurrect them and to say now you're an eidolon and you can inhabit this statue and move around, but sort of defend the honor of the god. And that would be a cool sort of afterlife for a character.

I don't know if the D&D, the first edition player's handbook, was intended to be an eidolon or not, but when we thought about, I think that was the thing that when we put that animated Moloch in Mordenkainen's, it was like, yeah. That next scene that you see as the thief is prying out the gem out of the statue of Moloch, the next scene is that statue coming to life and smashing them all to a pulp, as it would be.