The blue and red garment

Blue covers Red, indicating mankind's mission in the world: to temper the pressing qualities of Fire (red) with the serenity of Water (blue).

See also: the legs of the king of coins, ruler of daily life. Here, again, the blue leg covers the red.

Compare the crossed feet of the alchemist in the explanation for the eagle on the top right.

The X shape

The x-shaped binding of the wreath above and below refers to the natural philosophical rule once formulated by Heraclitus, according to which every development at its extreme point turns back toward its contrary.
(Compare the intertwined yin-yang symbol of the Taoists.)
The antique term for this was the chiasmus (Latinized from ancient Greek written with an X: χιασμός "crosswise, diagonal arrangement").

Significantly, in the Renaissance arrangement of the 22 tarot trumps, the continuous row changes direction at card X and the progression turns back to the starting point of XXI.

Discover this crucial reversal in the original Tarot order as you solve the interactive Four Elements Quiz Matrix

The Soul of the World

The female figure of the Soul of the World was an allegory of Plato and refers to the hidden source of all existence.

She brings the invisible creative power of the macrocosm into a state of dynamic readiness, from which the Four Elements then create the visible world - our human microcosm.

The blue-red veil alludes to the forces of Fire and Water, united in the background of Creation.

In this context, see the blue-red robe of the winged man on the upper left.

The Wand

The wand in the left hand of the Soul of the World is a symbol of fire, the primordial energy of the cosmos. (In other cultures called Chi, Ki, Prana ...).

The two poles of the wand above and below indicate that energy always arises from the connection of opposing forces. (like the electric current between plus and minus pole of a battery)

Wands also appear on two other trumps: in the hands of the Jester and the Juggler.

See 4 brief introductory videos: https://youtu.be/iiGbmJB6MY8

One eyed eagle & halo

The eagle on the position of the Air Element is the only one among the five figures on card XXI that has one eye only.

The characteristic quality of air is to divide. It manifests itself in man's urge to compare, to constantly judge, to doubt, to fear and try to be in control. With the image of a single eye, all compulsive division  is shown as overcome.

Compare the image of the one-eyed master below, his hands turned up and at the same time down, his feet crossed, and also shown one-eyed as a symbol for resting in the very quiet center of all contradiction.

It is this extraoridinary position, that earns the egle its halo, the intimate connection to the cosmic sphere, from where information is received without thought, judgment or prejudice: The mysic ideal of a then forbidden philosophical movement.

(Illustration from Atlanta fugiens by Michael Meier, natural philosopher, alchemist and personal physician of Emperor Rudolf II 16th century).

Regarding the same subject, see the blue-red robe of the winged man on the upper left.

Halo and wings

The halo of the human being occupying the position of the Water Element penetrates the picture's frame.

It is the image of the ascending master who has pacified (Water) in himself all destructive impulses (Fire), and is breaking free from the tormenting drive that determines the existence of ordinary people.

Compare the teaching of absolute non-violence by Christ, Buddha and the spiritual martial arts.

The wings express the achieved weightlessness of existence.

The phial

In its right hand the female figure holds a glass flask (phial), as it was used in the alchemists' laboratories for mixing ingredients.
This discovery was made by A. Jodorowsky and Ph. Camoin while analyzing hundreds of old Tarot cards.
The phial is a clear indication for the alchemical background of the first Tarot masters.

Hermes, God of the Sciences delivers a phiol for alchemical experiment.

Ox without halo

The ox in the position of the Earth Element lacks the halo that the other three figures are endowed with.

In the eyes of the philosophers of nature, the Gnosis, as well as the Buddhists, the devotion to materiality is corrupting man's spiritual liberty.

Nudity

On several Tarot cards, nakedness is an indication of NATURALNESS, of being connected to the creative and loving realm of Macrocosm.

People sacrifice their innate naturalness in order to experience daily drama in their life on earth. Their spiritual destiny however ought to be the return to naturalness.

In their sequence of the 22 trumps the Renaissance Tarot masters revealed the stages of this journey through which a soul may find the way back to its cosmic home. (In other cultures: the deliverance from the wheel of rebirths).

Legs crossed

Crossed legs, somewhat reminiscent of running or cycling, represent constant activity. In this case the constant combining of opposites, main objective of the Hermetic Arts ('As above so below'). 
Connected opposites, as between the plus and minus poles of a battery, generate energy and open up new potentials.
Crossed legs appear on several cards of the Tarot deck: on IIII, on the King of Coins – and reversed on XII as blocked movement.

The wreath

The wreath represents the antique symbol of the MANDORLA. Its special shape is created by the overlapping of two circles.

Formerly, the mandorla was a secret identifying emblem of early Christians, describing an intermediate position between two worlds.

Medieval representation of Christ, sitting within the mandorla, surrounded by the symbols of the Four Elements.

Sun & Moon

An often used alchemical symbol for the unification of opposites to form a new singularity.

The sun represents the impulsive qualities of the elements Fire and Air. The moon embodies the adaptive elements Water and Earth.
In the macrocosmic realm, this opposition (like all others) is suspended. This constitutes the 'paradisiacal' original state of creation.

LE MONDE

Card XXI - The World - contains the secret knowledge of natural philosophy and alchemy regarding the creation of our world from nothingness.

The blue-red veil of the World Soul

In Renaissance imagery, veils expressed concealment.

On the alchemist etching below, a scholar tries to discover the secrets of the shrouded Nature:

On this ancient Tarot card, the veil and wings denote the celestial sphere in which the World Soul dwells.

The globe on which she stands is divided into a lower earthly and an upper macrocosmic realm. Sun and the moon symbolized the hidden interplay of hot and cold qualities.

The red-blue veil explains the invisibility of the World Soul: Fire and Water are not yet separated items in her realm. Since there are no differentiations in Macrocosmos, therefore nothing can be perceived by the ordinary human mind.