The Qilin is bound by several chains and is tied to the mountain itself. It could move in an area I front of it by a couple of meters, but it only has a limited area of maneuverability. The enemies that it is facing outside of its range is struck down by either flames or lightning that its body generates.
The chains are also giving its body extra weight, so it is not as fast as it originally is. The soldiers of the House of the Azure Dragon are using this as a way to slowly chip the health of the Qilin. It would have been effective as a strategy, but the Qilin is using the lightning that the clouds above generate to heal itself from all the damage.
The Qilin is not even evading the attacks of the soldiers and just absorbing them using its tough scales. The ordinary soldiers could not carelessly approach the creature because of the flames that it is surrounding its body with.