Wonder Boy III: Monster Lair

The third game in the Wonder Boy series and the first in the Monster World sub-series.

The last Wonder Boy arcade game features two protagonists, Leo and Purapril (aka Priscilla), as they set off to free their land from a monster invasion.

Tropes in Monster Lair:

And Your Reward Is Clothes: Once you beat the game, you get to play through again wearing the Legendary Armor, with a higher difficulty level.
Big Boo's Haunt: Round 9 and 13.
Big Fancy Castle: The sixth stage. The prior stage has you ascending a mountain to reach the castle.
Blind Idiot Translation: The arcade version's ending text. "The invaders from the space were destroyed by your courageous fight..." The Megadrive's ending screen isn't much better.
Cyber Cyclops: The Round 13 boss.
Degraded Boss: The cactus-o-lantern boss returns as a Giant Mook in Round 13.
Direct Continuous Levels: Rounds 4-6, 9-10, and 11-14.
Dub Induced Plot Hole: The manual for the Turbo Grafx 16 version calls the protagonist Adam, but the high scores still show his name as Leo. Worse, the manual lists the Legendary Armor as the "Legendary Weapon of Complete Destruction".
Eternal Engine / Space Zone: Level 14.
Everything's Worse With Bees: Round 4 and its boss.
Gameplay Roulette: The first half of each round is Auto Scrolling platforming, the second half, where you fight the boss, is Shoot'Em Up.
Gaiden Game / Alternate Continuity: This picks up from the ending of the arcade version of Monster Land, where aliens steal the Legendary equipment. This is inconsistent with the SMS sequel, where Bock leaves it behind in the collapsing castle after being cursed, but regains it near the end of the game.
Green Hill Zone: Round 4
Hard Mode Filler: Stages 11, 12, and 13 are mainly rehashes of Stages 1, 5 (with a touch of 7's Slippy Slidey Ice World) and 9 (also iced over) respectively.
Ice Palace: Round 13.
Jungle Japes: Round 2.
King Mook: About half the bosses, including a giant snake, a giant bat, the Queen Wasp, a cactus jack-o-lantern, a Giant Enemy Crab, etc. The King Demon from Monster Land also returns.
Market-Based Title: The TurboGrafx 16 version drops the Wonder Boy III part of the title and is simply called Monster Lair. This does not apply to the PC Engine version, which still used the arcade game's full title.
Monster Town: Round 10 is a village inhabited by those mushroom mooks from Monster Land, and the boss is a giant version.
One-Winged Angel: The Final Boss does this after you slay his dragon.
Palmtree Panic: Rounds 1 and 11.
Shifting Sand Land: Level 8.
Slippy Slidey Ice World: Levels 7 and 12.
Underground Level: Level 3.
Wasted Song: The final stage is the only one with unique music. Also, most of the stages, as well as the boss battles, end before you get to hear the entirety of the music.
Wizard Needs Food Badly: Just like the first game.