When Lucifer looked at the Patriarch for a millisecond, the Demon Eyes quickly did its work and killed the Patriarch.
And when Lucifer was sure that the Patriarch was now dead, he closed his eyes and undid the Demon Eyes.
After all, he was basically forcing himself to use it. It would be in his best options to stop using it as soon as he was done.
And as soon as Lucifer closed the Demon Eyes, he...felt pain greater than before in his eyes.
No, it was not only his eyes but he could feel his brain getting stabbed with a million sharp needles at the same time.
Of course, that was not really happening, but the pain was equivalent to that.
However, that was not all as Lucifer could even feel his body...get a little bit thinner due to his body deteriorating over time when he forced himself to use the Demon Eyes.