Actually, when Ye Tianfan said this, he wasn't confident at all because in a Ten Directions realm battle, even the aftermath could directly destroy him. Even if Ye Tianfan had two extraordinary-level defensive magical treasures, he'd be either dead or wounded!
Tian Chu Zhenren wasn't a fool, so he didn't believe Ye Tianfan's words at all. He was even clearer than Ye Tianfan about the gap between the Ten Directions realm and the Thousand Source realm.
But there was no choice; Ye Tianfan had to be involved because his Illusory Fire was an indispensable factor. And since no one else could wield the Illusory Fire, there was no alternative.
Although Tian Chu Zhenren truly didn't want Ye Tianfan to go there, there was no recourse; Ye Tianfan had to go. Thus, Tian Chu Zhenren decided to quickly defeat his own foes and then closely monitor Ye Tianfan's situation!
