After the tacit agreement was reached, the vines of Poison Ivy entered into Meng Qiu's soul the exact moment that Blood Velvet buried his roots into the Spirit Tree.
The situation was easy to control for Poison Ivy, but it was not the case for Blood Velvet. Immediately after entering the Spirit Tree, he almost fainted due to the powerful soul force of the Spirit Tree!
Fortunately, Crystal Orchid was prepared, and stabilized Blood Velvet's body in time, hence the roots of the Blood Velvet were not separated from the Spirit Tree.
Even though the Spirit Tree was sealed at this moment, the power it contained was not something that any soul could bear. The Blood Velvet could only feel powerful surges of soul power constantly passed through his roots, which were buried in the Spirit Tree, to his whole body; the power was strong but very gentle, if not, his body would have exploded the moment he buried his roots into the Spirit Tree!