Spartoi

Spartoi (スパルトイ) are the guardian ghosts of Theodoros Alogospoulos.

About
They were Spartan skeletons. Just eight of the three hundred Spartans, that died fighting against the one million strong Persian armies at the battle of Thermopylae, were chosen by Theodoros to become his guardian ghosts. Each of their weapons were antiques, and their skeletal structures were imported samples.

Anime/Manga Difference
They appear in the manga series and the 2021 anime series but not in the 2001 anime series.