This Craft Essence can be obtained by bringing Mysterious Heroine X (Alter)'s Bond Level to 10. It comes at max level with all limit breaks.


When equipped on Mysterious Heroine X (Alter),
While she's on the field, Increases damage against Saber-class by 20%.



サーヴァントAUXヴォロイド“K6-X4”。 戦闘・航行の補助を目的としたサーヴァント支援用の 高機能ロボットだ。 X・オルタとは物心ついて以来の相棒で、 「黒騎士くん」と名付けられた。

性格は悪く、口も悪い。そも人前に現れない。 人間を完全に見下し、命令されてもまず無視するが、 X・オルタにだけは忠実に尽くす。

頭脳には微少なオルタニウム結晶が埋め込まれ、 X・オルタと同調している。 ちなみに、古代のヘルムを思わせるボディは、 過去、一惑星を焦土と化した暴虐の機械巨人の 頭部パーツが流用されているらしい。

「そうだったのか……可哀相。  ひどい仕打ちする人がいるものだね……」 「――――――」

His official designation is Servant AUX Voroid "K6-X4." He is a Servant auxiliary high-performance robot designed for combat and navigation assistance. A trusted partner of X Alter's for as long as she can remember, she nicknamed him "Black Knight-kun."

His character is mean and so is his tongue. He's not fit to appear in public. He completely looks down on humans and ignores orders as a matter of course, but he is loyal to the end to X Alter alone.

Minute Alternium crystals, synchronized with X Alter, are buried in his head. By the way, his body, which is reminiscent of an ancient helm, appears to be the repurposed head of a rampaging mechanical giant that once turned an entire planet into scorched earth.

"Is that so... poor you. There are some very cruel people out there..."