Youll come across Ifrit, Titan, Garuda, and Siren on your adventures. As for end game you have any of the dungeons post 40 so Dzaemal darkhold, Aurum Vale, Stone Vigil, The Wanderers Palace, Ampador Keep, and the dungeon at the end of the storyline Castrum Meridianum. Behemoth and Odin are both server fates too for high level.
A good site i found for stuff is :-
http://eorzeareborn.com/