How to create an NPC using eAthena's scripting:

map_name,x_cord,y_cord,npc_facing_direction -TAB- script -TAB- NPC Name#HiddenName -TAB- Sprite ID,{
   mes "[NPC Name]";
   mes "Hello World";
   close;
}

Common Script Commands:

Script Command Documentation:
All the script commands in eAthena can be found here.

How to enable your NPC:
1. Save it as a text file in your /npc/custom/ folder.
2. Open /npc/scripts_custom.conf
3. Add the following line:
npc: npc/custom/name_of_your_text_file.txt
4. Save and close.