go to : gameserver/data/script
and chek there if you have any rar files just open and edit that will make everyone monster in map to drop what item you want
for example : i have already Valentines Script
edit that and restart server
<Event ID="Valentines Event" Active="01 Jan 2010-20 Feb 2020">
<AllDrop Items="6392"
Count="15,50"
Chance="75%">
</AllDrop>
<Event ID="Valentines Event" Active="01 Jan 2010-20 Feb 2020">
<Droplist>
<AllDrop Items="6392"
Count="15,50"
Chance="75%">
</AllDrop>
</Droplist>
<Message
Type="OnJoin"
Msg="Event :All Monster in All Zone have chance drop Event - Medal , Rate now is: 80%">
</Message>
<Npc ID="12371">
<Condition>
<Inventory Items="4209-4217" Count="1" Operation=">="></Inventory>
</Condition>
<Take>
<Item Items="4209-4217" Count="1" Type="OfEach"></Item>
</Take>
<Give>
<Item ItemID="4625" Count="1"></Item>
<Item ItemID="1540" Count="10"></Item>
<Item ItemID="728" Count="10"></Item>
</Give>
<SystemMessage
Msg="Congratulations. Receive your item.">
</SystemMessage>
</Npc>
<EventEnd>
<Take From="AllPlayers">
<Item ItemID="4209-4217"></Item>
</Take>
</EventEnd>
</Event>