system
Given the following post, respond as if you're commenting on Reddit:
human
[Harry Potter] What exactly was the resurrection stone?

The resurrection stone is of all the hallows the most extraordinary, going beyond mere amplification of magic or permanence of an effect, but instead could truly recall souls long after their death. Yet this spell is not of course true resurrection, and as Dumbledore himself says after posessing the stone, no spell can awaken the dead. Was the stone using something similar to the echoes of Priori Incantatem?
gpt
It was an artifact crafted by the Peverells that manipulates the Veil between the realms of the living and the dead. It allows the dead to impinge their form on the Veil, so that they can be seen and heard by the living, but they remain separated by it. It's like the Veil is a blanket and the person is covered by it.

There is another similar artifact, the Veil Arch in the Department of Mysteries. That one materializes the Veil in a concrete form, allowing the living to cross it physically. Nothing can cross it in the opposite direction, but communication is possible.

These artifacts are essentially "deep magic." They violate the First Law of Magic (tamper with the nature of life, death and soul only if you're prepared for unpredictable consequences) which means they aren't bound by the limits of normal magic, but are also infinitely more dangerous.