That thin shadow was twisting and turning to completely hide under the shadows of the broken rocks. If not for the Magic Array catching that trace of a different aura, he wouldn't have discovered Birbo's hidden move.
It was a simple Shadow Binding using the shadow of the caster's opponent to restrict their movements. That spell was an 8th Tier Spell, and its effect wasn't very visible.
Powerhouses of the same rank would take less than a second to struggle free, and the shadow mages would suffer a magical backlash from it that would definitely last more than a second.
If the Shadow Mage wasn't able to eliminate their target within a second, they would usually die.
But now, that small time frame appeared at a deadly time!
Lin Yun was about to struggle free of the Shadow Binding after less than half a second when some gravity enveloped his body. The sharp increase in gravity distorted the Law Runic Shield around Lin Yun, and his bones cracked it.