Shadow on the Moon

Anyone who could construct a stable Spell Model could become a Wizard — that was the Wizards' ultimate secret! Having been given a new life as the son of an aristocrat and armed with a super quantum computer from his past life, Spell Models game as easily as breathing to Merlin. With this overwhelmingly huge advantage, would Merlin become the greatest Grand Wizard of all time?

EndlessFantasy Translation 

A Wizard's Secret

J_Squared

When the Ninth-level Darkness-type Spell Model was fused, all the Spell Models vibrated gently. A black mist wrapped around the Spell Model as it underwent gradual changes. Finally, the black mist dissipated, and formed a black ball of light with the appearance of a heart.

Merlin was immediately reminded of the Wizard Heart wielded by Saturn and Rael when they were facing the powerful Progenitor's Body. That was the foundation of the Great Wizards, a multicolored ball of light formed by combining all the Spell Models in their bodies.

Right now, except for the color, in terms of aura and shape, Merlin's black ball of light was no different from the Great Wizards' Wizard Heart.

The Six-Elemental Wizard Heart