He could use it however he wanted, right up until the Mirror Image's Spiritual Power was completely drained.
But during that time, his own Spiritual Power had to be continuously consumed to maintain the Mirror Image's very existence.
This meant that if his own Spiritual Power ran out, the Mirror Image would vanish just as it had before—even if it had just appeared and merged with him at full power.
The Spiritual Power of the Mirror Image and his own could not be fused.
Otherwise, he could just keep summoning and fusing indefinitely, giving himself a limitless supply of Spiritual Power!
If that weren't the case, with his Tai Chi Cultivation, he could have worn the Qiu Ape down to death all by himself. He wouldn't have needed Li Shifan to help.
'Oratory? Tea Dao? Summoning?'
'I've been dead for all these years... have the Inner Sect Disciples of the Celestial Spirit Sect all become this monstrous?'
