Roche Frain Yggdmillennia

One of the “Black” Masters. Thirteen years old, and the youngest skilled magus of the “Black” Masters excluding Caules. His character concept is something like “a pupil and his teacher who he doesn’t really disagree with, but fatally misunderstands.” His talent with golem-making techniques stood out above the rest from a young age and he made even further leaps and bounds after he received the transplant of his family’s Magic Crest.
When he summoned Avicebron, he privately thought that “he wasn’t anything great” at first, but he couldn’t help being moved by the overwhelming beauty and toughness of the golems that Avicebron made. After that, he became Avicebron loyal pupil—but he never expected that Avicebron would go as far as to take his life.
Even when he heard from Avicebron that exceptional Magic Circuits were needed as the core to “Golem Keter Malkuth: Royal Crown, the Light of Wisdom,” he didn’t pay it any mind, never thinking that “he himself” fit those conditions.
In that case, what should Roche have done in order for him and Caster of “Black” to have understood each other better? Unfortunately, there was no means of saving him from his fate besides ordering Caster to kill himself with a Command Spell. One of these two in this Master-Servant pair would have to die without exception.
Though it was a summoning done with a catalyst, this Master and Servant are extremely compatible in terms of mentality, but their respective trends and way of thinking were both too extreme.
Incidentally, if you were to ask why Roche is the only character that was made thirteen years old… my memories are fuzzy, but I think the Giant Robo OVA that I own was the cause. For good or ill, the idea of a remote control robot (as in, Testsujin) stuck to me.

Fate/Apocrypha material: Fate/Apocrypha Encylopedia