What's the use of Sivir M's combo slot being full?

Did you learn "Memory of the Soul" by Lao Sai? If the combo slot is full, you can recruit, that is, temporarily turn to some former allies, such as female demons, demon archduke and others (maybe you haven't met them yet); If you turn off the "soul memory" in the passive skill bar of Lao Sai, then when the combo slot is full, an animation will automatically appear, which can crit, and it will be very useful to play the arena in the future.

The skill of "the memory of the soul" is specially used to recruit people, but it is useless to recruit people. I learn it mainly to save some time when fighting monsters. After all, the animation lasted for a few seconds. . . After playing the arena, you still have to turn off your soul memory.