Lion's Eye Diamond

Set
Mirage
Rarity
Rare
Text
Discard your hand, Sacrifice Lion's Eye Diamond: Add three mana of any one color. Activate this ability only any time you could cast an instant.
Legality
Legal in: Commander, Duel, Legacy
Restricted in: Vintage
Rulings
2004-10-04: The ability is a mana ability, so it is activated and resolves as a mana ability, but it can only be activated at times when you can cast an instant. Yes, this is a bit weird.