Conquest of the Crystal Palace is an outstanding gem in the NES-Library. Despite its low profile, I would put it in the same category as titles like Kick Master, Shatterhand and Vice: Project Doom. Games that really pushed the system hard, but didn't get the recognition they deserved until years later. The insane level of difficulty towards the end is a little off-putting, but it doesn't ruin an otherwise great game.
The story of the conquest of the Crystal Palace
Years ago, the kingdom of the Crystal Palace was conquered by the evil Zarras. The only ones who managed to escape were Zap, the keeper of the crystal palace, and little prince Farron. Now a teenager, Farron has returned to take back his kingdom with Zap in tow.

The origin
Conquest of the Crystal Palace is interesting for a number of reasons. Not just because it's a good game, but also because of its pedigree. It was developed by Quest, who later developed the Ogre Battle series and the even better known Final Fantasy Tactics. It was the first game worked on by Yasumi Matsuno, who would go on to have a long and successful career at Square Enix. In retrospect, the game received a decent amount of press but has largely kept a low profile. Don't miss the game because it's a great but difficult action title.

Three gems
Before starting Conquest of the Crystal Palace, you have a choice of three gems that grant you a special ability. The Life Crystal permanently increases your maximum health. The flying crystal gives you a higher jumping power. The Spirit Crystal gives your sword the ability to shoot fireballs. Although you can only choose one, the other two are available as temporary items in the game stores.

feudal and modern
In many ways, Conquest of the Crystal Palace is reminiscent of Konami's Goemon. Both are set in feudal Japan, but also mix in modern technology like televisions and the like. However, while Mystical Ninja has some light RPG elements, Crystal Palace is entirely action-oriented. In addition to the crystals, there are a large number of additional power-ups. Some are dropped by enemies, but you can purchase most at Kim's Astral Mart. These range from health and extra lives to new sub-weapons, some of which work particularly well against certain bosses. Money is never really a problem as there are many places you can mine it indefinitely. Also, there are at least two shops per level to balance the game.

Zap
The most interesting mechanic in Conquest of the Crystal Palace is Zap. Zap can fight at your side at any time and has its own health bar. He is very effective against normal enemies and aggressively attacks everything on the screen. If you have the whistle, he can perform a more powerful dash attack. The bosses are a different story. Zap can land a few loose hits on most bosses, but goes down fairly quickly as his AI isn't particularly smart. It's important to manage his bet so you don't have to spend coins to bring him back to life. While you can ignore this mechanic entirely, it makes the second half of the game less tough.
levels and opponents
Conquest of the Crystal Palace is a very inconsistent game. The first two levels are very easy, with many enemies to accumulate money. You can fully heal yourself and still have money left over for weapons. From about level 3, the game is turned off. The screen is routinely crowded with enemies, to the point of extreme slowdown and flickering. Unfortunately, the second half of the game isn't as well designed or balanced as the early stages, which drags the game down a bit. The number of sudden traps and obstacles such as rising fire and vicious enemy spawns also increases significantly. There are a number of blind jumps and "gotcha" moments that are only there to rob you of your extra lives, and it's not fair. It's really amazing how much the game is changing, and not for the better.
The level of difficulty
The difficulty of Conquest of the Crystal Palace increases so much because the game is not that long. With five levels, the game is quite short overall. It would be too if it wasn't so ridiculously difficult towards the end. Don't forget that the US version has been toned down from the original! If they had evened out the difficulty curve, the game would have been really great.
Conclusion
It's a bit sad that Conquest of the Crystal Palace has garnered so little attention. The level of difficulty is relatively high, but that's no reason to give up. A nice little hidden gem.
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