Maple story what does shadow partner do

Shadow Partner is a skill for Hermits (which are assassins [thieves]). You need 1 summoning rock per each time you use it. The time it lasts varies on the skill level. When used, it imitates or shadows any skill you use.
For example: If I use shadow partner, then lucky seven (lucky seven = throw two stars at the same time) then the shadow will throw two stars as well. So it's like I'm throwing 4 stars.
If shadow partner is used with triple throw multiple times (Night Lord skill - a Night Lord is a thief-assasin-hermit) then it looks like a huge line of stars.