There are 23 Tarot cards, each with different effects. Most of them first appear in Boktai 2.
 Green or Blue Cards
Green cards and blue cards are one use consumables and are mainly found in Dream Avenue.
 The Fool
Card of potential. Restart an area from the beginning.
This is meant as a way of freeing yourself if you somehow get trapped in a block puzzle. Using this card counts as a continue. The Dark Card can also be used for the same effect at the cost of soll.
 The Lovers
Card of choice. Recovers all Energy.
When used, either Lita or Carmilla will appear next to Django on the status screen as your energy refills. Carmilla randomly appearing is probably a bug - perhaps she was meant to show up if and only if you are currently controlling Sabata.
 The Emperor
Paternal card. Protects from all properties for a given time.
The effect lasts 30 seconds. It does not negate damage, only reduce it.
Card of justice. Inflicts loss of Life back onto nearby enemies.
Spiked balls fall and all enemies onscreen take damage equal to the amount of health you've lost.
 The Hanged Man
Card of sacrifice. Swaps Life and Energy.
Card of death. Restores Energy in exchange for Life.
Card of harmony. Carries out maintenance for selected weapons.
All currently equipped weapons are fully repaired, if they have damage meters.
 The Devil
Card of desire. Summons darkness bugs.
 The Tower
Card of havoc. Hurts nearby enemies and yourself based on level.
Spiked balls fall and everyone onscreen takes damage.
 The Star
Card of hope. Exchanges an item in your bag for a brand new one.
Picks a random item and resets its freshness meter. It may end up choosing an item that doesn't spoil, having no effect.
 The Moon
Card of anxiety. Summons moon bugs.
 The Sun
Card of happiness. Summons solar bugs.
Card of revival. Restores full life when down to zero.
 Red Cards
Red cards boost stats permanently. A limited number of them are found in various green chests.
 The High Priestess
Card of intelligence. Raises Spirit.
 The Empress
Maternal card. Raises Vitality.
 The Chariot
Card of victory. Raises Agility.
Card of courage. Raises strength.
 Wheel of Fortune
Card of destiny. Raises Status.
Affects a random stat for a two point boost.
 Gray Cards
Gray cards are key items. The three sages are used to open the Aqueduct, while The World is a trophy.
 The Magician
Card of creation. One of the 3 Sages.
 The Hierophant
Card of mercy. One of the 3 Sages.
 The Hermit
Card of pursuit. One of the 3 Sages.
 The World
Card of Achievement.
Obtained upon obtaining all titles.
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