Chaos Cards:
Chaos cards are a Special Type of card, they are kept separate from your Deck or Extra Deck. They have a Special Card Back (Dark Grey with a Golden Compass Rose), and and the front of the card is completely black, except for a Symbol drawn in white. You can only use Chaos Cards on your turn, you can use 1 Chaos Card when your Life Points are below 1 of 3 numbers, refereed to as Thresholds (4000, 2000, 1000), these do stack, so if you have 3600 Points you can use 1 Chaos Card, if you don't and then take 1700 damage, you now have 1900 and can use 2 cards.

Threshold List:
4000 and Lower
2000 and Lower
1000 and Lower

Other uses:
Chaos Cards can be used in 2 other ways, Countering and Breaking.
Countering with a Chaos Card: If you take a direct attack and the damage would reduce your Life Points to below a Threshold, you can instead reduce your Life Points to the Threshold to negate the attack, then play a Chaos Card. (IE: You have 4900 Life Points, if you would take 2000 damage from a direct attack, you can instead reduce your Life Points to 4000 to play a Chaos Card).
Breaking a Chaos Card: Sometimes your cards just aren't going to save you. On your turn you can use a Chaos Break to deal with a Major Threat. To use a Chaos Break you first reduce your Life Points to the next Threshold, then you select 1 of your Chaos Cards, that card is rendered useless for the rest of the duel. If you use a Chaos Break you can then remove from play any card on the field. You can only use a Chaos Break on your Main Phase.
WARNING: Countering and Breaking count as using a Chaos Card, so if you reduce your points to 4000 to use one you still cant play a Chaos Card on your turn.

Choas Card Format:
Name of Card: (The name of your Chaos Card)
Symbol:  (Describe or provide a picture of the Symbol on the front of the Chaos Card)
Threshold: (Most Chaos Cards can be used at 4000 or lower. You can trade this off for a stronger card by choosing 2000 or 1000 [Can only be used at 2000/1000 or less Life Points[)
Duration: (A Chaos Cards effect doesn't last the entire duel, it needs a limit as to how long it lasts. Some examples include: 3 Turns, 2 Attack, or after you use the effect 4 times, etc. Use 'Instant' if the effect is an effect that works when you play the card and has no effects after that.