request this script..

[rko123]

satan morroc spawn in morocc every 3 hours, has a Gm option can start the event.. and put a announce whos mvp.. item prize can modify by admin 99 .. thankss

[Nameless2you]

http://rathena.org/wiki/Permanent_Monster_Spawn

If I think correctly then there is no way to make the monster drop another item via a script, you can only make it give an extra/additional item, if you want the monster to drop a specified item you'd have to change that in the mob_db.txt, but considering you probably want to keep the original drop you'd have to make a duplicate of the monster.