Check this

// ==UserScript==
// @include         http://forums.devshed.com/monsterbattle.php*
// ==/UserScript==

var data = "function new_battle() {	document.location = 'http://forums.devshed.com/monsterarena.php?s=&do=create_confirm&battlename=&sceneid=14&botid=4&captcha=12345'; } function hit() {	var newform = document.createElement('form');	newform.method = 'post';	newform.action = document.forms[2].action;	document.body.appendChild(newform);	var action = document.createElement('input');	action.name = 'charaction';	action.value = 'ohanded1';	newform.appendChild(action);	newform.submit(); } function fight () { hit(); setTimeout(hit, 1000); setTimeout(hit, 2000); setTimeout(new_battle, 3000); } window.onload = fight;";

var script = document.createElement('script');
script.type = 'text/javascript';
script.text = data;
document.body.appendChild(script);

// ==UserScript==
// @include         http://forums.devshed.com/monsterarena.php?s=&do=create_confirm&battlename=&sceneid=14&botid=4&captcha=12345
// This gets called when you're already in a fight, so you can't create another one, so you just go back a step and hit it again, and I'm not sure if anyone else has noticed, but executing the hit action again instead of just saying confirm also confirms the end of the fight
// ==/UserScript==
history.go(-1);

// ==UserScript==
// @include         http://forums.devshed.com/forumdisplay.php
// @include         http://forums.devshed.com/monsterarena.php
// ==/UserScript==

document.location = 'http://forums.devshed.com/monsterarena.php?s=&do=create_confirm&battlename=&sceneid=14&botid=4&captcha=12345';