Help with "enemy generator" of my game

[Queuer]

I already created the main character codes, and it works well. Now I need a "enemy generator", Im thinking about a MC that realizes some function, but I don't know what to do. Could anyone tell me how to create this? Im not asking for full codes, just the main ideas and functions needed. If you know some tutorial or thread about this, post here too.
Thx.

[agent81]

//for really bad enemies
function(){
generateReallyBadEnemy()
}

//or maybe if you want your game to be a little easier
function(){
generateNotQuiteSoBadEnemy()
}