After a boss defeat, absorb its Arcana and equip it to use its spell. Castlevania: Belmont's Curse tarot cards belong to the deck Rose inherited from her mother, with cards linked to powerful monsters. After you defeat The Fallen in Paris Streets, the absorption phase lets you claim its power before choosing your equipped spell.
How do you absorb and equip Arcana after a boss defeat?
Hold the absorption button after the fight, then open the Equipment menu and replace your currently equipped Arcana with the spell you want.
Absorb the defeated Arcana
During the absorption phase, hold the button shown on screen. With Xbox button prompts, this is RB. You will see a glowing orb beside Rose and an instruction along the bottom of the screen to absorb the Arcana's power.

Replace your equipped spell
Open Equipment, select your currently equipped Arcana, then choose another spell from your Arcanas collection. Each Arcana has a unique spell; absorbing and equipping it lets you use that power in combat.

The Fallen Throw sends out a corrupted cross that damages enemies it hits. It returns to Rose after traveling a certain distance or hitting a wall, so take nearby walls into account when choosing where to throw it.
Where do you find Tarot clues for the next Arcana?
Open the Tarot menu to review discovered clues and Arcana, then use those clues to plan where to go next.

The cards' links to monsters let Rose discover clues about how or where an Arcana can be reached. Open it when you are not sure where to go next.
How do Works of Mercy and Blessings improve Arcana?
Complete an Arcana's Works of Mercy to obtain Blessings, then use Purify to improve it.

Each Arcana has two or three Works of Mercy, each a specific task. For Cursed Flame, hit with the spell 20 times to complete the displayed task and gain a Blessing. Select Cursed Flame in the Arcanas menu and hold the displayed Purify button. Its improvement fires a bigger fireball that slightly pushes back its target.
Does Castlevania: Belmont's Curse turn bosses into friends?
The Fallen becomes a captured monster inside Rose's tarot card, speaks to her, and lets her use its powers after the card frees its mind from a curse.

After the fight, Rose notices that one of her mother's cards has changed. The Fallen card now carries the monster's picture, and Rose hears its voice inside her head. Their conversation also points her toward the other guardians holding keys to the catacombs. See the bosses page for who they are.
Can Tarot cards give you movement abilities?
Yes. After obtaining The Fallen's power, you can grab sharpened anchors to pull yourself toward them and reach other platforms.

With Xbox prompts, aim at the anchor using the left stick, then press RT to propel yourself toward it. When a platform is too high to reach by jumping, look for an anchor you can target.
Every boss you beat adds another card like this. The walkthrough shows where to find the next one.