The Heroic Spirit, meanwhile, also resolved himself as he held back the magical energy worming its way into him.
This mage is dangerous.
He did not see Bazdilot expending his final Command Seal as folly. He had realized that, although it did not show in his expression, the mage was taking his life in his hands. He was gambling his whole existence in order to transmute the Heroic Spirit into something else.
Whatever order he gives with his final Command Seal, I must at least eliminate this man.
Even the Heroic Spirit was not able to grasp the nature of the power eating into him. If he was not careful, however, this corrosion could spread to the other Heroic Spirits who had been summoned for the Holy Grail War. Even as he desperately suppressed the curse from his own lifetime welling up inside him, the great hero remained noble.
I must stop him. I must stop the wicked tyrant who would dominate this era.
Even as the mental pollution passed a point that would likely drive most Servants mad, this great hero still reached out his hand, not to defend himself, but for the sake of the other Heroic Spirits and the inhabitants of this era, who he had not yet even met. He did not care if he was called unprincipled. He did not care if he was called a mad spirit that turned his hands against his own Master. The man famed as a hero among heroes was determined to throw even his own honor to the winds, and slay the mage in front of him for the sake of someone he had not yet seen.
Then, just as he had shaken off the mental pollution and his hand was about to reach the mage’s neck... Bazdilot spent his last Command Seal, as if to sneer at the hero’s nobility.

Fate/Strange Fake: Volume 3, Interlude ("The End of Escape")