The erratica beast will drop a throw knife for its rare drop and the succubus will drop a cestus for its rare drop. The Succubus is also a semi-slow mob and drops a scroll of escape as its second most rare drop. I'd guess at a rate of 7-10% for the drop rate of the scroll.If you warp from the DE town to the northern forest and then run Southwest to the mountain line you will find large spawns of Dark Succubus and erratica beast. Both are passive mobs which is nice because you can log in and out without worry of danger. The erratica is lvl 18 and the succubus is 20. 

Since this area is not by any dungeons or cities it is hardly camped at all. I've gone hours without seeing anyone, but I've also found people who like this area but it doesn't matter if they are there because there are so many spawns in the area. Its also easy to get here because of the gatekeeper warp is fairly close. One note, if you use a scroll of escape it will take you to gludio instead of back to the DE village. You will have to run back up to the tent area where you warped in if you want to go to the DE village. Its about a 1 minute run.