Unlockables
- For the different gameplay modes available after beating the game, see the Getting Started page.
Rare monsters
These are two hard-to-find monsters that give you a lot of experience and/or very rare items. The areas that the monsters appear in are accessible relatively early in the game, but the monsters themselves won't actually appear until after you defeat Camilla.
Skeleton Medalist
The Skeleton Medalist is in a small room off the side of the pit that Dracula throws you down at the start of the game. There is a room in the Underground Warehouse that borders on the pit. Directly below that room is the Skeleton Medalist's room, and directly below that room is the entrance. Use the Roc Wing 
to fly upward, whipping at the wall until you find it. Go in, grab the power-up, and then hit the ceiling until you find the secret entrance.
The Medalist isn't particularly strong, however it is incredibly fast. Use the stopwatch as an Item Crush to stop it and then beat it to death. It is possible to get into this room with the Kick Boots 
however there is no point as the Medalist won't be there until after you finish the Underground Waterway.
- EXP: 1500
- Item 1: Toy Ring
(does nothing) - Item 2: Bear Ring
(Pluto/Black Dog turns you into a bear instead of a skeleton)
See http://castlevania.classicgaming.gamespy.com/cotm/ for more on the Bear Ring and what it can do.
Lilith
Lilith is in a hidden room on the western wall in the Underground Warehouse. In the large, vertical chamber there are three visible entrances. Between the top and middle ones is a breakable wall. You can get a power-up here as well, even before Lilith shows up. She resembles the Fallen Angel and Succubus enemies and attacks with energy balls. She's strong, but beatable. Use Uranus/Thunderbird to hit her without being hit, and make the fight end more quickly than if you tried to whip her to death. Once she dies, wait for your MP to recharge and repeat the process. Not only can you get of the best pieces of armor in the game from her, but she also gives 20,000 experience points.
- EXP: 20,000 (24,000 if you have Pluto and Mandragora active when she dies)
- Item 1: Mind Ex
- Item 2: Sage Robe
(+250 Def, +500 Int)
Lilith appears as a wind demon in Mesopotamian mythology and as a Adam's first wife in Jewish mythology. Either could be the basis for the CotM creature.
Glitches
DSS Card tricks
Non-existent card combinations
It is possible to use combinations of cards that you haven't found yet. Select a card combination that you actually have. When you activate the DSS, Nathan flashes from normal to black to glowing yellow. As soon as he goes to black, pause the game. In the DSS menu, select the combination that you want to use, and then unpause. You have now activated the combination that you just selected. This will last until you deactivate the DSS, at which point you will have to redo the glitch from the beginning.
Stat-boosting
Some card combinations boost stats like strength, intelligence, and defense considerably when activated, others have no effect or even reduce your stats. You can exploit a glitch to make attacks stronger by swapping cards in mid-use. This really only works with summoned creatures as they are on the screen long enough. To perform the trick, equip the combination to get the summon that you want to use, and then use it. While it is being summoned, equip a combination that boosts strength. The game will determine damage based on current strength, not your strength when you started the summon.
The other time when this is highly useful is when using the Item Crush ability (Pluto/Salamander combination). As soon as the Crush starts, switch to a strength-boosting combo to do additional damage.
Curing poison
When you activate the Jupiter/Black Dog card combination, it puts you in a poisoned state, and when you deactivate the combo, it gets removed. That is to say, the system sets your state to normal when the DSS is deactivated - not to what it was before you activated the combo. That means you can cure status aliments like poison by activating and then quickly deactivating the combination. You can even use the combination even if you don't have the cards yet.
The Battle Arena
Magic in the Battle Arena
When you enter the Battle Arena, all of your MP is drained and if you restore your MP, it gets drained again. However, it takes a moment for all of your MP to disappear, so if you are fast enough you can get off a spell. Summons are the only spells that can do enough damage with a single casting, however it takes a moment to enter the button combo to use it, so you need to have far more MP than is required to actually cast the summon. Practice the combo before entering the Arena so you don't slip up and waste mind restores.
Repeat the last room of the Battle Arena
After you finish the last fight of the Battle Arena, you get the Shinning Armor and slide through the gap, back into the entrance. However, if you aim just right, you'll slide into the next screen without falling down the gap. From here, you can turn around and slide back into the room with the armor. The door will be open, allowing you to go back and fight the Devil again. Since the Devil gives 30,000 experience points per kill, this is a fairly fast way of leveling up.