User blog comment:Jopjopjop/Volume 20 Spoilers/@comment-16281343-20150718042050/@comment-16281343-20150718044800

"(I am guessing only the kings get to use it)."

Yes. That's because already reincarnated Devils cannot use it. There is still the "no mixing of pieces" rule.

Ajuka also said that those reaching the top without using the King piece are mostly reincarnated Devils.