What would be the best way for a supernatural entity to fit into a physical body smaller in mass and volume?

Question

Angels are advanced technological beings who are messengers of the gods. These extra-dimensional beings are large, upwards of 30ft tall, and resemble eldritch abominations in their true form, such as three faces, wheels, wings, etc. As they are monstrous and terrifying in appearance, they take physical human form when they enter the material realm. They can travel between realms, but cannot control a human body from their realm, and must be present in the world in order to have any impact on it. Specially built physical bodies are built to house them so they can interact with mortals without giving them a heart attack from fright.

It stands to reason that for a being of that size, it would naturally have to take a form of similar size. The problem is that thirty foot tall beings walking around is not productive for a relationship with humans. These physical forms must be human sized in order to interact on a regular basis. therefore, an angel's physical form would have to squeeze into a body with a much smaller mass, volume, and size.

What would be the best way for an angel to make this possible?

Answer 1

The human they present as, is actually a hyper-dimensonal object.

Consider: The diagonal of a square is 1.4...(square root of 2). So a 1.4 foot 1 dimensional line can fit in a 1 foot square.

More applications allow a $\sqrt3$ line to fit or a 1 x $\sqrt2$ plane.

So your human shape is the 3 dimensional cross section of a higher dimensional object.

Answer 2

Aethir.

Known to the ancients of Greece, Aether (after a god of the same name):

pure upper air that the gods breathe...

According to Epiphanius, the world began as a cosmic egg, encircled by Time and Inevitability (most likely Chronos and Ananke) in serpent fashion. Together they constricted the egg, squeezing its matter with great force, until the world divided into two hemispheres. After that, the atoms sorted themselves out. The lighter and finer ones floated above and became the Bright Air (Aether and/or Uranus) and the rarefied Wind (Chaos), while the heavier and denser atoms sank and became the Earth (Gaia) and the Ocean (Pontos and/or Oceanus).

Known to the science of medieval times, it was considered to be "compressible":

also called quintessence, is the material that fills the region of the universe above the terrestrial sphere...

Medieval scholastic philosophers granted aether changes of density, in which the bodies of the planets were considered to be more dense than the medium which filled the rest of the universe.

In more modern times Albert Einstein:

sometimes used the word aether for the gravitational field within general relativity

He is quoted as saying:

"We may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an aether. According to the general theory of relativity space without aether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this aether may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time."

Conclusion.

They've never told us, but they presumably either deflate; releasing the Aether, summoning more to regain their true form.

Alternatively perhaps they rely on being able to compress it - much as the medievals or Einstein might suggest regarding Lorentz field contraction. But in a way that we don't currently understand - a way that reduces mass.