Illidan is afraid of Maiev Shadowsong because they have a feud and Maiev Shadowsong wants to kill Illidan.
During the Ancient War, Illidan was both a hero and a repeat offender of the night elves. In pursuit of powerful power, he turned to the enemies of the night elves, the demons of the Burning Legion, and later for Tyrande. He betrayed the Burning Legion and helped the night elves, and finally betrayed the night elves to create a copycat version of the Well of Eternity for his own selfish desires. Maiev Shadowsong witnessed the entire behavior of Illidan and hated him deeply.
After Illidan was rescued from the dungeon by Tyrande, Maiev led the Watchers to hunt down the escaped Illidan. However, during the pursuit, the Watchers were almost wiped out, which deepened the Maiev hated Illidan, so she followed Illidan through the Dark Portal to Outland. Although he was captured again, he was eventually rescued by Kael'thas and Vashj during transportation.
The origin of the name of Illidan's Warblade of Azzinoth
"Azzinoth" is the most powerful Eredar. By chance, he accepted Sargera The power of Si, but this power did not corrupt Azzinoth. He once killed countless demons with the "Wrath of Argus". Later, he met Illidan when Illidan was young and became Illidan's teacher. Taught Illidan how to use various magics.
Azzinoth used evil energy and his own weapon "Wrath of Argus" and used all his power to pour into this double blade and ended his life, sending the weapon away before death. Given to Illidan, Illidan named the double blades in honor of this mentor: "Warglaives of Azzinoth".