Pasted

// https://rathena.org/board/topic/107501-custom-skill-npc/
 prontera,155,175,5	script	Sample#skill_upg	4_F_KAFRA9,{
	.@skill_lv = getskilllv( .skill_id );
 	mes "You got LV "+.@skill_lv+" Skill";
	if ( .required_item[.@skill_lv] )
		if ( select( "Upgrade","Cancel" ) == 1 ) {
			if ( countitem( .required_item[.@skill_lv] ) ) {
				delitem .required_item[.@skill_lv],1;
				addtoskill .skill_id,1,0;
				mes "Done.";
			}
			else {
				mes "You need "+getitemname( .required_item[.@skill_lv] );
			}
		}
	close;
 	OnInit:
		.skill_id = 1234;
 		setarray .required_item,
			21218,
			21219,
			21220,
			21221;
		end;
}