I couldn't miss the chance to practice my drawing!
The memories and emotions of people, housed inside crystals... These are visions. By summoning forth the visions of ages past and worlds distant... We can call upon their strength in battle.
Visions (ビジョン, Bijon?) are the physical manifestations of memories and emotions stored within the crystals of Lapis, the setting of Final Fantasy Brave Exvius. Described as the "hopes and dreams of legendary warriors given life", visions are bound to their crystals and can only be summoned by those with the "power of visions" (ビジョンの力, Bijon no Chikara?), an ability held by the game's main characters Rain and Lasswell.
As a general rule, a vision is created when a person's memories is collected inside a crystal upon their death. Death is, however, not essential to the process; intense emotions (such as Charlotte's worry over her comrades, or Lawrence's admiration) may crystallize and generate visions while the owners continue living. Furthermore, the possibility of becoming a vision is not limited to the inhabitants of Lapis alone; memories may originate on distant worlds—namely, those depicted throughout the Final Fantasy series.
Visions trascend the boundaries of time and space to manifest in the world of Lapis, as seen in the Arena, as crystals of Lapis not only contain memories from other worlds, but also memories of other timelines.
Gameplay-wise, visions are "units" (ユ二ット, yunitto?), or playable characters that may be used to battle if included in a party. With the exception of Season One's story characters (Rain, Lasswell, Fina, Lid, Nichol, Jake and Sakura), all units are visions, and will perform one or more particular roles: Physical Damage, Magic Damage, Hybrid Damage, Tank, Healing, and Support. In most cases, they must be summoned by using either Friend Points, Rare Summon Tickets, or Lapis, the game's premium currency. The exception to this are Raid Summons (obtained by reaching a certain amount of points during the eponymous raids or by spending raid coins on their respective banners) and some special units awarded upon the completion of a mission, such as Maxwell or the different Trust Moogles.
The power of invoking visions was developed in Paladia, a world of crystals whose inhabitants hold the power of visions from the time they are born. This power was passed onto the people of Lapis in the aftermath of Hess' secession attempt from the technological Aldore, and the subsequent civil war between the two factions. About 700 years ago, Hess, defending its the "visionary magicks" (a power born from scientific progress, different to preexisting magic), was led by its Eight Sages, while Aldore's lieutenants were the Sworn Eight of Paladia. However, the leaders of Aldore betrayed their own soldiers and banished the entire battlefield to Lapis through a massive dimensional gate.
The force generated by the land passing through the gate was tremendous in scale, destroying nearly half of Lapis in the process. It also allowed crystals to grow in certain areas. After many battles between the Paladian soldiers and the people from Lapis who had survived the catastrophe, most Paladians chose instead to live side by side with the native inhabitants, mixing their bloods. In the current era, many of Lapis' inhabitants have some Paladian ancestry, due to which they have the potential to access the power of visions (which simply lies dormant within them).
Rain and Lasswell, knights from the Kingdom of Grandshelt, are prompted by a girl encased in crystal, Fina, to safeguard the Earth Crystal from Veritas of the Dark. At the Earth Shrine, the two knights confront the aggressor, but they are swiftly defeated by Veritas. He destroys the Earth Crystal and leaves, but Fina reappears before the two knights, and grants them the power of visions so that they may save the world. Although Lasswell can also summon them, Rain's control of the ability is far superior than his brother's; this can be seen in the several special events that involve ephemeral versions of other worlds.
In Chapter III, Nichol is surprised to find that the the two knights have the power of visions, stating that he has read records of warriors using them—though such records spoke of such warriors as servants of the darkness, pawns used by demons. Later on, Nichol changes his opinion in regard to this power; after using the Water Crystal to save Aquapolis Olderion, the party returns to the city to tell Arsha of Elle's passing. Rain then summons Elle's vision so that they can see each one last time.
During Chapter V, Veritas of the Light summons two soldiers to her aid while battling Rain's party at the top of Mysidia Tower, and once again during the battle at Misma Pass in Chapter VI. During the same chapter, when Veritas of the Frost forces the battle to battle among themselves to determine who is strongest, most of the party members summon visions in their aid. Sakura calls forth Marie and Roselia, Fina calls forth Chizuru and Hayate, Nichol is aided by Charlotte and Lawrence, while Lasswell invokes Wilhelm.
At the Vision of Bahamut event, it is revealed that espers can create visions of themselves with their own memories and if someone manages to defeat one esper vision, the original creature will be weakened.
During Chapter VIII, as the party traverses the Land of the Crystals, Raegen shows Sophia's vision to their sons, Rain and Lasswell, so that she may have one last look at them now that they have grown. At the Eternal Summit, Sol is able to summon forth a vision from within the crystal tower, the Chaotic Darkness, said to be born from the evil that lurks in humanity.