There is Dream of Mirror Online. Its a VERY good MMORPG. It also has a main storyline, and hard bosses. Strong pets and the whole game is free. You can get Classes. There's mage, swordsman, fencer, Martial Artist, hunter, etc. You can fly on your weapons after beating a certain quest, but the quest boss is hard. It takes alot of skill to fight, not just clicking. You usually need a team to beat bosses. The game was imported from Japan, so not all classes are in. Evolution 3 pets are rideable.