He is also imbued with the power of darkness, and can change into a vampire after he builds up a Trance (shortened to TRC in-game) meter by fusing with his Terrennial, Nero, which allows him to absorb life out of his foes.

Unlike Lucian, Aaron has light powers, and can temporarily become an avatar of the sun when needed by fusing with his Terrennial, Toasty.

The ultimate goal in Lunar Knights is to destroy a number of boss vampire enemies, in which the basic mission is to defeat each of them in their respective dungeons, either by exploiting their elemental weakness or using Trance.

Once this is accomplished, the boss is launched into space using the Casket Rocket, Laplace; the player then enters a minigame consisting of three parts.

There are four different terrennials available besides Nero (Dark) and Toasty (Sol): Ursula (Flame), Tove (Earth), Alexander (Cloud), and Ezra (Frost).

There are five types of weather: balmy subtropical, tropical rainforest, humid continental, arid desert and frigid arctic.

Terrennials are the physical manefestiations of the elements that accompany the characters, with fire, ice, wind, and earth represented.

When these terrennials are equipped, the player can use TRC powers, and they will add their elemental attacks to weapon strikes, at the cost of some energy.

This option gives the player more of an advantage: slotting a GBA game into the DS' W-Gate allows the player to use extra sunlight by adding the detected sun strength to the amount produced by the in-game weather system (the extra sunlight appear as green blocks in the game's sensor bar) for a certain amount of time.

Lucian, the Lunar Knight overhears them, and sets out to obtain the whereabouts of the Duke, the leader of the Dark Tribe vampires.

Returning to the Mansion, Lucian refuses to help Bea free the prisoners, claiming they would not even try to fight back against enemies.

After defeating and purifying the Poes, Lucian and Aaron obtain Alexander and Tove, terrenials of Wind and Earth.

Lucian and Aaron travel through the castle, and discover that the enemy pilot they encounter in space during purification levels is Perrault, Nero's other half.

The terennials question their goals and wonder if their battle is right, eventually deciding that the humans are smart enough to save their world, the duo find themselves in the throne room.

After defeating the Duke, Polidori absorbs him, informing the duo that the ParaSol was really the Planet Eater, a planet-destroying weapon.

The Knights defeat Polidori, and Dumas appears to tell them that the Immortals will arrive to stop the renegade Earth.

Django and Sabata fight Ox Fire, one of the enemy FM-ians from the original Mega Man Star Force, as a hidden boss.

Players can also obtain exclusive items by transferring game data from Mega Man Star Force into Boktai DS.