Instructions
Use an MPQ Extractor such as the aptly-titled "MPQ Extractor" to extract the file " NightElfAbilityFunc.txt" from the MPQ file titled "war3x.mpq."
Search for "Starfall life drain" then change the line "Targetart= [path of ability model]," naming the .mdl or .mdx file that holds the model for the new starfall missile effect. Save "NightElfAbilityFunc.txt."
Navigate to the folder with "NightElfAbilityFunc.txt," right-click and copy or cut the file, then right-click the "war3x.mpq," file and select "Paste." This injects the file back into "war3x.mpq," which you can test by opening "Warcraft 3" and casting the Starfall spell with a Night Elf hero.