This game is hard as nails. Battle of Olympus is an old NES action/RPG that is highly overlooked. It copies a bit of Zelda 2, but it has improved a lot of it greatly. You play an unnamed hero out to prove yourself to the Greek gods of old. Frack the storyline, though. This game is the shit. This must be one of the very first implementation of a Metroidvania gameplay. Much as I hate using that term, that is the best description of the gameplay of this game.
Like I said above, this game is very difficult. I feel that this game is even more difficult than the NES Crystalis. The most dangerous creatures in this game are the small bats, slime, and maybe the birds. Don't worry about boss fights like the Cyclops or Hydra. If you are man enough to survive the little pests, you will have no problem dealing with the bosses for the most part.
The video above is a Let's Play series for this game. As you can see on the 12 episodes, this game is a killer. You can die in levels where you face small but speedy enemies. The screen in some of the levels gets fast and furious even if you are equipped with the best sword in the game.
I have not yet finished the game. I have to load save states multiple times to even get through a lot of the stages. I'm now going for the Pegasus, which is no small task as you can see from video 5 of the Let's Play series.
I'm still charging my Dingoo as I write this post, so it will be some time before I can get back to the game. If you are a retrogamer, this game will satisfy your Action/RPG cravings. It's hard and frustrating, but you will not be able to drop your controller.
Edit: I beat the game after a thousand loads of save states. Any idea what NES games I can play now? I'm planning to play Castlevania 3, Dragon Warrior, or Zelda 2.