I got this idea from Digimon.  These cards are based off of Japanese mythology of the 4 guardians of Kyoto: a turtle, a dragon, a phoenix, and a tiger, each of them from a different direction.  They aren't in any specific order.
 
Genbu, the Black Turtle of the North
(Water/Aqua/8/2000/3500)
Effect:  Increase the ATK of this monster by 500 pointsfor every "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West"
 
Seiryuu, the Blue Dragon of the East
(Wind/Dragon/8/3000/2000)
Effect:  Increase the ATK of this monster by 500 points for every "Genbu, the Black Turtle of the North", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West"
 
Suzaku, the Crimson Phoenix of the South
(Fire/Winged Beast/8/2800/2500)
Effect:  Increase the ATK of this monster by 500 points for every "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", or "Byakko, the White Tiger of the West"
 
Byakko, the White Tiger of the West
(Earth/Beast/8/2700/2700)
Effect:  Increase the ATK of this monster by 500 points for every "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", or "Suzaku, the Crimson Phoenix of the South"
 
Sacred City- Kyoto
(Field Spell Card)
Increase the ATK of "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West" by 500 points.  Also, "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", and "Byakko, the White Tiger of the West" cannot be targeted by Spell Cards.  Also, if any of the monsters are destroyed in battle, you can Special Summon it onto the field by paying half of your Life Points.  Also, downgrade any "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", and "Byakko, the White Tiger of the West" in your hand and on the field by 2 Levels.
 
Offerings to the Guardians
(Spell Card)
This can only be activated if "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West" is in you hand.  When this card is activated, you cannot summon any monster in the same turn (including Flip Summon and Special Summon). You may choose one of the following effects:
-Remove 2 WATERr monsters from your Graveyard from play to Special Summon "Genbu, the Black Turtle of the North."
-Romove 2 WIND monsters from your Graveyard from play to Special Summon "Seiryuu, the Blue Dragon of the East."
-Remove 2 FIRE monsters from your Graveyard from play to Special Summon "Suzaku, the Crimson Phoenix of the South."
-Remove 2 EARTH monsters from your Graveyard from play to Special Summom "Byakko, the White Tiger of the West."
 
Sacred Temple Barrier
(Trap Card)
If your opponent attacks "Genbu, the Black Turtle of the North", "Seiryu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West" on your side of the field, negate the attack.
 
(Side note: In case you were wondering why I mentioned temples, it's because there are lots of temples surrounding Kyoto because of the 4 guardians)
 
Spirits of the Guardians
(Spell Card)
You can only activate this card if "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", and "Byakko, the White Tiger of the West" are in your Graveyard.  You opponent must discard 4 cards from the top of his/her Deck.
 
Cardinal Directions
(Spell Card)
Pay 2000 Life Points to search your Deck for "Genbu, the Black Turtle of the North", "Seiryuu, the Blue Dragon of the East", "Suzaku, the Crimson Phoenix of the South", or "Byakko, the White Tiger of the West" and add it to your hand.  Your Deck is then shuffled.
 
Izanagi, the Lord of Life
(Fusion/Light/Warrior/12/5000/3500)
"Genbu, the Black Turtle of the North"+"Seiryuu, the Blue Dragon of the East"+"Suzaku, the Crimson Phoenix of the South"+"Byakko, the White Tiger of the West"
Effect:This monster can only be special summoned by removing from play the above monsters on your side of the field. You do not use “Polymerization” to special summon this monster from your Fusion deck. Increase the ATK of this monster by 1000 points if "Sacred City- Kyoto" is face-up on the field.  This card is unaffected by any Spell or Trap Cards.  You cannot Normal, Flip, or Special Summon any cards while this is on the field.