Dr. Golden "Preparation":

~ We'll become as "The One"! You'll put me back together! I'll become Immortal!
You'll Boost up my possibilities! You're my Key to Victory! You're the SOULtion!

No one will stop Me ever again! Mwa~ha~ha~ha!

Dr. Golden "Preparation" has used the Phantom Ruby to turn Silent "The Player" into the Soultion, so he can absorb the Protagonist and finally... achieve his Goal.

Silent "The Player" is a "Solution" for the Main Antagonist of gaining control over everything, restoring back his human form and overall... becoming unstoppable!

Remnant substitute in FNaS: Fiercy Forces 🠖 Soul + Solution = Soultion

For the specific, it's Soldier Grandeur Silent
(Silent's "The Player" an upgraded metamorphosis of hers "Job System")
in hers Spirit form, that was imprisoned by Dr. Golden "Preparation".
She is called: Soultion Silent.