Onmyoji can possess multiple Shikigami, but the number of Shikigami they can command at the same time is limited.
If they do not issue commands and leave the Shikigami to attack freely based on instinct, facing the world's first-rate Transcendents would be no different from courting death.
Therefore, to maximize the advantage of a summoned creature horde, it is necessary to have at least ten or more Shikigami coordinate their attacks to form a sufficiently powerful threat.
However, the corresponding problem also follows: Shikigami from different Onmyoji do not consider each other when attacking and will not intentionally avoid harming each other.
It was not until the Yin Yang Bureau later developed the "Hundred Ghosts Night Parade Great Formation" that this issue was resolved.
