Try this one :
- script Sample -1,{
OnInit:
setarray .mob_id[0],1002,1113,1399,1159;
set .size, getarraysize(.mob_id);
set .random, rand(.size);
set .amount, 1; // amount of monster spawned
set .monster, .mob_id[.random];
end;
OnMinute00:
OnMinute30:
monster "prontera",150,150,getmonsterinfo(.monster, 0),.monster,.amount,strnpcinfo(0)+ "::OnKill";
announce getmonsterinfo(.monster, 0)+ " has been spawned in prontera",0;
end;
OnKill:
announce "The monster " +getmonsterinfo(.monster, 0)+ " has been killed",0;
end;
}
Screenshot :