Wonder Boy in Monster Land/Round 3

Part A

 * 1) You begin on the right side of the entrance hallway of the castle, and must proceed to the left.  As you do, you will be introduced to red spirits.  In the arcade and PC Engine versions of the game, they float left and right, and will descend to your level.  In the Sega Master System version, they bob up and down and do not adjust their height to make it easier for you to hit them.  They will not drop money, but they do drop good point items for you to collect.  Jump up the steps to reach part B

Part B

 * 1) Drop down and jump over the spikes in the floor as you run to the left.  Climb up the ladder to the level above.  You will see a bar in a higher section, but unless you've been seriously injured, you can ignore it.
 * 2) Prepare to deal with a mushroom descending the steps as you move back to the right.  Then climb up the ladder to reach the next section.  Continue to climb up, and jump to the left before climbing any higher.  You will find a skeleton to fight who may drop the whirlwind special weapon if you defeat it. (You will only find Cobras in the SMS version.)
 * 3) You can ignore the shop behind door B as well.  Walk back to the right and jump along the platforms.  Watch out for the skeleton who occupies the high ledge.  It's possible than it may jump all the way off to the floor below.  Then proceed to the left until you reach a series of steps.
 * 4) A mushroom will be dropping down the steps as you climb them.  An hourglass will also appear as you get near the top.  While the SMS version provides you with a ladder to climb up, other versions enable you to reach the next level by way of a spring loaded into the floor.
 * 5) Along the top level, the game will notify you of something strange.  If you push up around the "!" label on the map, you will discover a hidden armor shop.  It is a good idea to spend 60 gold on the Light Armor.  After you exit, prepare to deal with a goblin standing by a conveyor belt which will be moving left.  Defeat it, and then proceed to the right end of the hallway to part C.

Part C

 * 1) Part C is very much like a more crowded version of Part A, with many more red spirits to deal with.  Defeat them all to collect the point items they provide, and drop down to door C.  When you're ready, head inside for an encounter with the stage boss.

Boss
This red knight is the first knight of many that you will encounter throughout the game. Learning the best method to defeat them early on will help you in later stages of the game as well. A knight will only swing his sword while jumping. You should fear getting jumped on top of more than you should fear getting stabbed. The best strategy to use against knights is an aggressive one. Rush the knight and swing your sword just as you are about to make contact with the knight. Keep putting pressure on him, and he will eventually be forced to jump over your head. Allow him to do so, and then turn around and immediate press your attack again. You should be able to strike him faster than he is able to respond, and keep him on the ground until his back is against the opposite wall. The red knight will only take a handful of swings to defeat, provided you collected the Broad Sword from the previous stage. Once he is defeated, he will drop eight coins and no key. Simply collect all of the coins to advance to the next stage.

Arcade/PC Engine

 * After climbing the steps to part B, jump to the right from the top step to make a coin appear.
 * After crossing into part B, jump to the left from the ledge to make a coin appear.
 * When you reach the right most platform inside the castle around where the skeletons appear, jump along the wall to make a coin appear.