During Wendy and Nyx's fight, Nyx had used a skill called [Holy Speed!], which greatly enhanced her agility and made her a formidable opponent. Currently, Nox didn't possess many skills in his arsenal, only Shadow Oblivion and Phantom Cloak. Both were offensive skills, but Nox needed something to complement his battle style.
As a close-range fighter, Nox needed to be fast and agile to take out his enemies and escape if they proved too strong. A speed-related skill would have allowed him to get away unscathed when he encountered Goliath, even increasing his fighting chance slightly.
Nox hated that he couldn't keep up with Goliath's speed. It reminded him of Hendrix, who was also fast. Subconsciously, to eliminate this weakness, he had been searching for a good target with a speed-related skill.
Fortunately, during the fight with Wendy, Nyx had used Holy Speed! Nox knew he couldn't miss this chance to get rid of his weakness.