Castlevania Legends (known in Japan as Devil's Castle Dracula: Dark Night Prelude) is a 2D action horror platformer developed by KCE Nagoya and published by Konami for the Game Boy in March 11, 1998.
Set as a prelude to the Castlevania franchise, the game puts players in 1450 as Sonia Belmont (mother of Trevor Belmont) who sets out to destroy the evil Count Dracula with help from Dracula's deserted son, Alucard.
Castlevania Legends is one of the few Castlevania stories that was officially retconned out of the official timeline after Koji Igarashi was given creative control of the franchise. He later produced Castlevania: Lament of Innocence as the new origin of the timeline.
Castlevania Legends packs in many more game mechanics than either of its predecessors did, perhaps combined. Along with the upgradeable whip and rope slide featured in Castlevania II: Belmont's Revenge, Sonia is offered the following abilities:
Burning Mode - pressing both buttons renders Sonia invincible for a short period of time, and gives her the ability to do double damage. This ability is limited to once per life on a given stage and is governed by a countdown meter.
Crouching Walk - Sonia can pass through low barriers by walking forward as she crouches. This is the same ability Simon Belmont has in Castlevania IV for the Super NES.
Soul Weapons - Sonia can use five different magical attacks, which take the place of the traditional sub-weapons in Castlevania lore and the mere two sub-weapons from Belmont's Revenge. Instead, the Axe, Holy Water, Cross Boomerang, Dagger, and Time Stopper are special collectibles that you need to find in order to get the "real" ending.
Air Control - Unlike the 8-bit Belmonts featured in games prior, Sonia has some amount of air control while jumping. There's not quite enough to allow her to easily jump onto a platform directly over her head (though it may be possible with precision timing), but it does offer the player enough to avoid some enemy contact or prevent overshooting a jump.
Castlevania Legends also offers vertically-scrolling areas, where the majority--if not all--of the previous two games achieved vertical progression screen-by-screen.
The level design is mostly linear but has some path divergences where you can find the aforementioned special collectibles, one-ups, et cetera. These divergences are more than single-screen hidden areas, such that you'll veer off the beaten path for a short distance, though not enough to get you lost. There are also trap areas triggered by striking certain candles, landing you into a pit of respawning zombies that you must continue to slay until they're all gone, at which point you're returned to the room above.