You'd need to change the special attacks flags for the NPC
https://code.google.com/p/projecteqq...nxa_Karnkvi.pl
Here is an example of doing that. Basically this mob at 75% goes inactive and spawns 3 mobs, when these 3 mobs die, the mob goes active again.
https://github.com/EQEmu/Server/blob.../npc.cpp#L1402
You can find what the letters mean there