[quote=@Xeiyenreisha]
<Snipped quote by LunarStandard>

Cannot be Special Summoned. While face-up on the field, this card is also DARK-Attribute. Once per Chain, during either player's turn, when a Spell Card, Trap Card, or monster effect is activated: This card loses exactly 500 ATK and DEF and that activation is negated. When this card is destroyed and sent to the Graveyard: Target 1 monster in your Graveyard (if possible); destroy all cards you control, also Special Summon that monster (if any).
[/quote]

The ruling's [url=http://yugioh.wikia.com/wiki/Card_Rulings:Light_and_Darkness_Dragon]here[/url] if you don't want to take my word for it and would rather have something more official.

"The effect of "Light and Darkness Dragon" only activates when a Spell/Trap Card is activated from the hand or flipped face-up. It cannot be activated when the effect of a Continuous Spell Card, Continuous Trap Card, "Ojamagic" or a Spell Card sent to the Graveyard by "Destiny HERO - Diamond Dude" are activated."

EDIT: Already done, Eklispe.