Servant of Gordes Musik Yggdmillennia as part of the Black Faction in the Turifas Holy Grail War of Fate/Apocrypha.

Saber's identity is Siegfried, the Dragon-Blooded Knight (竜血の騎士), the hero portrayed as the main character of the German Nibelungenlied epic. Prince of the Netherlands, he wields the precious sword Balmung which he received from the Nibelungen family, and has fought in many campaigns and adventures. His most well known feat is killing the evil dragon Fafnir. He then bathed in the blood of the dragon, and has obtained an invincible body.
(Source: Type-Moon Wiki)