Moku entire vision filled with giant fist that coming closer with unbelievable speed. He sometime thinks why their giant body can move with that kind of speed. Moku only can blame it to mana who become their source of power.
After thinking it again, Moku realized that Deak shouldn't have enough mana to control dozens of treants like this. Moku didn't have time to think about this because he was so panicked by their gigantic bodies and after that, they were beating him to a pulp. But this time he still had time to look at them with his inner eye.
It turns out that it's not Deak's mana that controls them but these treants move by using their mana inside their bodies. Deak's spell is simply a trigger for mana in the treants' bodies. Maybe with his spell, he can change the way the mana inside the trees works so they can transform into the treants.