Help in NPC_INVISIBLE

[Yonko]

something weird on the source of the npc_invisible i try to use this as a custom skill but weird things when used it drains SP of user at super fast time i didnt know the what this means, i sense this is the reason why the skill drains SP faster

case NPC_INVISIBLE:
        //Have val4 passed as 6 is for "infinite cloak" (do not end on attack/skill use).
        clif_skill_nodamage(src,bl,skillid,skilllv,
         sc_start4(bl,type,100,skilllv,0,0,6,skill_get_time(skillid,skilllv)));  --> //here
        break;